Pharmaceutical antibody compositions with resistance to soluble cea

ABSTRACT

The present invention relates to pharmaceutical compositions for the treatment of an epithelial tumor in a human, said pharmaceutical composition comprising an IgG1 antibody specifically binding to human CEA, wherein the variable region of said IgG1 antibody comprises at least (i) a CDR-H1 having the amino acid sequence “SYWMH” (SEQ ID NO: 29) and a CDR-H2 having the amino acid sequence “FIRNKANGGTTEYAASVKG” (SEQ ID NO: 28) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO: 27) or (ii) a CDR-H1 having the amino acid sequence “TYAMH” (SEQ ID NO: 31) and a CDR-H2 having the amino acid sequence “LISNDGSNKYYADSVKG” (SEQ ID NO: 30) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO: 27). Furthermore, processes for the production of said pharmaceutical compositions as well as medical/pharmaceutical uses for the IgG1 antibody molecules bearing specificities for the human CEA antigen are disclosed.

More than three decades have passed since Gold and Freedman first described the tumor associated carcinoembryonic antigen (CEA) in human colon cancer tissue extracts (Gold and Freedman; J. Exp. Med. 122 (1965); 467-481).

Meanwhile, 28 other genes/pseudogenes relating to the CEA gene family have been discovered. In an attempt to simplify the nomenclature used for the members of the CEA gene family, the family has recently been renamed the “CEA-related cellular adhesion molecules” (CEACAMs) and the nomenclature for its members has been unified (Beauchemin, Exp. Cell Res. 252 (1999), 243-249). For example, according to this nomenclature, human CEA (CD66e) is termed CEACAM5.

The human CEA gene family is clustered on chromosome 19q13.2 (Olsen et al. Genomics 23 (1994); 659-668). Its 29 genes and pseudogenes can be divided into three subgroups, i.e. the CEA subgroup containing seven expressed genes, the pregnancy-specific-glycoprotein (PSG) subgroup containing eleven expressed genes and the third subgroup which contains only pseudogenes (Hammarström, Sem. Cancer Biol. 9 (1999), 67-81; Beauchemin, Exp. Cell Res. 252 (1999), 243-249). The analysis of the amino acid sequences of CEA and the other family members revealed that they belong to the immunoglobulin (Ig) superfamily (Williams and Barclay, Annul. Rev. Immunol. 6 (1988), 381405). All members of the CEA subgroup are attached to the cell surface membrane: Biliary glycoprotein (CEACAM1; BGP1; TM-CEA; CD66a), CEA gene family member 1 (CEACAM3; CGM1; CD66d) and CEA gene family member 7 (CEACAM4; CGM7) have hydrophobic transmembrane domains, whereas carcinoembryonic antigen (carcinoembryonic antigen-related cell adhesion molecule 5; CEACAM5; CEA; CD66e), non-specific cross-reacting antigen (CEACAM6; NCA; NCA-50/90; CD66c), CEA gene family member 2 (CEACAM7; CGM2) and CEA gene family member 6 (CEACAM8; CGM6; CD66b) are linked to the plasma membrane by glycosylphosphatidylinositol (GPI) lipid moieties. The CEA proteins are highly glycosylated with a molecular weight of up to approximately 300 kDa, depending on the number of Ig domains.

As regards the biological activity of the CEA proteins, in vitro studies with tumor cell lines suggested that several CEA subfamilies including biliary glycoprotein, CEA and non-specific cross-reacting antigen can act as homophilic and heterotypic cell adhesion molecules when expressed on the tumor cell surface (Oikawa et al., Biochem. Biophys. Res. Commun. 186 (1992), 881-887; Zhou et al., Cancer Res. 53 (1993), 3817-3822). More recently, a possible role of CEA and non-specific cross-reacting antigen in the innate immune defense protecting colon from microbial attack has been discussed (Hammarström and Baranov, Trends Microbiol. 9 (2001), p. 119-125). In particular, it has been proposed that these proteins bind and trap microorganisms preventing them from reaching and invading the epithelial cells of the microvilli.

It was hypothesized that CEA is an oncofetal antigen which is expressed during fetal life, absent in the healthy adult and re-expressed in cancer. However, CEA is also expressed in normal adult tissue. For instance, biliary glycoprotein, CEA, non-specific cross-reacting antigen and CEA gene family member 2 are expressed in normal human colon, particularly in the mature columnar epithelial cells facing the gut lumen and in the highly differentiated cells at the crypt mouth (Frängsmyr et al., Cancer Res. 55 (1995), 2963-2967; Frängsmyr et al., Tumor Biol. 20 (1999), 277-292). More specifically, these proteins are localized to the brush-border glycocalyx of the mature colonocytes lining the free luminal surface. Biliary glycoprotein, CEA and non-specific cross-reacting antigen are also expressed in a number of tumors of epithelial origin (Hammarström, Sem. Cancer Biol. 9 (1999), 67-81; Shively and Beatty CRC Crit. Rev. Oncol. Hematol. 2 (1985), 355-399).

Already in the late 1970s and early 1980s, CEA became a favored target antigen for radioimmunolocalization of colorectal and other epithelial tumors. This is due to the fact that CEA is overexpressed in 95% of gastrointestinal and pancreatic cancers, as well as in most small-cell and non-small-cell lung carcinomas. It is also expressed in breast carcinoma and squamous cell carcinoma of the head and neck (Primus et al., Cancer 42 (1978), 1540-1545). In fact, CEA is one of the most extensively used clinical tumor markers. It is used as a serum tumor marker for colorectal and some other cancers due to its stability, its fairly restricted expression in normal adult tissue and its high expression in tumors of epithelial origin. The bulk of CEA in a healthy individual is produced in colon. There it is released from the apical surface of mature columnar cells into the gut lumen and disappears with the feces. Thus, only very low levels are normally seen in the blood from healthy individuals. For instance, CEA levels in the blood of healthy individuals is less than 2 μg/l. In contrast, CEA levels in serum from patients with colorectal and other carcinomas are increased, ranging up to more than 2000 μg/l (Thomson et al., PNAS 64 (1969), 161-167). In particular, progressive, malignant, or late stage epithelial tumors are frequently accompanied by high serum concentrations of soluble CEA (Fletcher; Ann. Intern. Med. 104 (1986), 66-73). It is known that components from the plasma membrane, including CEA, are continually exfoliated from the surface as plasma membrane-derived vesicles (Taylor and Black, J. Natl. Cancer Inst. 74 (1985), 859-866; Sack et al., J Clin Invest. 82 (1988), 586-93) which through draining lymph and blood vessels can end up in the blood. As the tumor size increases, more CEA will accumulate in the blood. The main use of serum CEA determinations as a tumor marker is in the post-surgical surveillance of colon cancer. Increased CEA levels was the first indicator of recurrent disease in 81% (Minton et al., Cancer 55 (1985), 1284-1290) and 89% (Wanebo et al., Surg. Gynecol. Obstet. 169 (1989), 479-487) of patients, respectively. Serum CEA levels can also be used as a prognostic indicator (Mulcahy and Benson, Curr. Oncol. Rep. 1 (1999), 168-172).

Due to its over-expression in many epithelial cancers CEA is not only used as a tumor marker but also as a target for anti-tumor therapy. For example, gastrointestinal cancers account for a large proportion of human epithelial tumors, with an estimated 21.700 new cases of gastric cancer and 135.400 new cases of colorectal cancer in the United States in the year 2001 (Greenlee; CA Cancer J Clin 51 (2001), 15-36). Colorectal cancer is the third most common malignancy and the third leading cause of death from cancer in both males and females (Ries; Cancer 88 (2000), 2398-2424). In an attempt to find new therapeutics against these tumors, anti-CEA monoclonal antibodies have been explored as possible therapeutics for CEA-positive cancers (Murakami et al., Immunol. Invest. 25 (1996), 23-35).

One example for an approach in which patients with low tumor load (corresponding to low serum CEA levels) have been successfully treated is a study performed by Behr et al. In this approach, a ¹³¹I-labeled variant of labetuzumab (labetuzumab is a humanized form of anti-CEA monoclonal antibody MN-14; Behr et al., Cancer, 94: 1373-1381, (2002), 1559-64) has been analysed in a phase II trial in which 30 CRC patients with small volume metastatic disease chemorefractory to 5-fluorouracil and folinic acid or in an adjuvant setting after liver metastasis have been enrolled. A single injection of ¹³¹I-labeled labetuzumab was given. Of 19 assessable patients, 3 had partial remissions and eight showed minor responses up to 15 months in duration. In the adjuvant setting, 7 of 9 patients were disease free for up to 3 years, whereas the relapse rate in the control group was 67% in the same time period. The serum CEA levels of the patients ranged from 3.9-45 ng/ml (Behr et al., Cancer, 94: 1373-1381, 2002). In another study characterized by patients with low CEA serum levels (<5 ng/ml), CEA radio-immunotherapy with ¹³¹I-labetuzumab (loc. cit.) has been shown to improve survival post salvage resection of colorectal cancer metastases in the liver. 23 patients received a dose of 40-60 mCi/m² ¹³¹I-labetuzumab. Five-year survival was 51.3% for treated and 7.4% for control groups, respectively (Liersch et al., JCO, 2005, ASCO Proc, Vol 23, No 16S: 3627).

Yet, therapeutic approaches dealing with high serum CEA concentrations frequently resulted in low or no anti-tumor responses. For example, Wong (Clin. Cancer Res. 6 (2000): 3855-3863) used a genetically engineered ⁹⁰Y labeled human/murine chimeric IgG T84.66 antibody with high affinity specificity to CEA in a phase I radioimmunotherapy trial in order to evaluate said antibody in patients with metastatic CEA-producing malignancies. 22 patients received one treatment cycle (only 3 patients had 2-3 cycles) consisting of a diagnostic administration of ¹¹¹In labeled antibody followed by ⁹⁰Y labeled chimeric antibody. No major anti-tumor responses could be found. 16 patients generated human anti-chimeric antibodies (HACAs). The range of soluble CEA levels in the patients enrolled in this study was 14.8-1027 ng/ml (median 97 ng/ml). In a follow-up study, the same antibody was used in a combination therapy with 5-Fluoro-uracil (5-FU). In this Phase I combination trial, 21 patients with chemotherapy-refractory metastatic colorectal cancer received 5-FU and ⁹⁰Y-cT84.66. No objective responses were observed. The mean serum CEA level was 227.4 ng/ml, ranging from <2, 5-1305 ng/ml (Wong, Clin Cancer Res, 9 (2003): 5842-5852). In another study by Hajjar et al., iodine-131-labeled humanized MN-14 anti-CEA monoclonal antibody has been evaluated in patients with metastatic gastrointestinal and colorectal cancer. In this phase I trial, 21 patients either after prior external beam radiation or after standard chemotherapy have been treated with antibody. 7 of 21 patients had human anti-human antibodies (HAHAs), but no adverse effects. No antitumor response was observed. Again it has been found that elevated plasma CEA levels prevent a therapeutic effect of anti-CEA antibody approaches (Hajjar et al., Clin Colorectal Cancer, 2 (2002), 31-42).

In view of the problems set forth above, the provision of means and methods for efficient therapeutics for progressive, malignant, or late stage epithelial tumors is highly desirable.

Accordingly, one aspect of the invention relates to a pharmaceutical composition for the treatment of an epithelial tumor in a human, said pharmaceutical composition comprising an IgG1 antibody specifically binding to human CEA, wherein the variable region of said IgG1 antibody comprises at least the amino acid sequences selected from the group consisting of:

(a) a CDR-H1 having the amino acid sequence “SYWMH” (SEQ ID NO. 29) and a CDR-H2 having the amino acid sequence “FIRNKANGGTTEYAASVKG” (SEQ ID NO. 28) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27); and (b) a CDR-H1 having the amino acid sequence “TYAMH” (SEQ ID NO. 31) and a CDR-H2 having the amino acid sequence “LISNDGSNKYYADSVKG” (SEQ ID NO. 30) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27).

The amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponds to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7 (Chester, Int. J. Cancer 57 (1994), 67-72; Harwood, Br J. Cancer. 54 (1986), 75-82).

In a preferred embodiment of the pharmaceutical composition of the invention, said variable region of the IgG1 antibody defined herein comprises a CDR-L1 having the amino acid sequence “TLRRGINVGAYSIY” (SEQ ID NO. 34) and/or a CDR-L2 having the amino acid sequence “YKSDSDKQQGS” (SEQ ID NO. 33) and/or a CDR-L3 having the amino acid sequence “MIWHSGASAV” (SEQ ID NO. 32).

Determination of CDRs is known to the person skilled in the art; see e.g. http://www.bioinf.org.uk/abs/#cdrid. Numbering of amino acid sequences in antibodies can be carried out e.g. according to the Kabat numbering scheme described in the art; see e.g. Kabat, E. A., T. T. Wu, H. M. Perry, K. S. Gottesman, and C. Foeller. 1991. Sequences of Proteins of Immunological Interest, 5th ed. Bethesda, Md.: National Center for Biotechnology Information, National Library of Medicine.

The present invention provides means and methods particularly suited for the treatment of (an) epithelial tumor(s) in patients with high soluble CEA concentrations in their serum/plasma. Such high soluble CEA concentrations are found in the serum/plasma of epithelial tumor patients with progressive tumors, recurrent, metastatic, late stage tumors and for patients with high tumor load/burden. It has been found that IgG1 antibodies specifically binding to human CEA which comprise a variable region as defined above not only bind to CEA-positive target cells, but also to soluble CEA; see Example 5 of the present invention. Surprisingly, although binding to soluble CEA, the IgG1 antibodies of this invention kill CEA-bearing tumor cells, even in the presence of high concentrations of soluble CEA. Put in other words, said IgG1 antibody constructs are not inhibited by soluble CEA in their cytotoxic activity (antibody-dependent cell cytotoxic activity; ADCC) against CEA-positive tumor cells. For instance, Example 5 shows cytotoxic activity against Kato III cells (CEA-positive human gastric carcinoma cell line) of CEA-reactive IgG1 antibody constructs as defined above in the presence of increasing amounts of soluble CEA antigen. Thus, cytotoxicity mediated by the IgG1 antibodies as defined herein is resistant to soluble CEA. The IgG1 antibodies of the present invention as defined herein comprise a variable region with CDR-H regions as set forth above, including the CDR-H3 “DRGLRFYFDY” (SEQ ID NO. 27) amino acid sequence corresponding to Kabat positions 95-102 of murine monoclonal antibody A5B7 (Chester; Harwood; loc. cit.). This monoclonal antibody also binds both to membrane-bound and soluble CEA (own data). It has been found that the amino acid sequence “DRGLRFYFDY” mediates resistance to soluble CEA when used in the variable regions of humanized anti-CEA IgG1 antibodies as defined herein; see Example 5.

In contrast, as shown in Example 2, huIgG1 CEAII-mediated cytotoxic activity is inhibited by increasing amounts of soluble CEA. The variable region of huIgG1 CEAII is derived from mAb T84.66 (Neumaier, Cancer Res. 50 (1990), 2128-2134). Since huIgG1 CEAII has been found to bind to soluble CEA, it was concluded that soluble CEA antigen prevents the antibody from exerting its antibody-mediated cytotoxic activity. In light of the results obtained for T84.66-derived IgG1 constructs, it could not be expected that soluble CEA does not inhibit cytotoxic activity in A5B7-derived antibody constructs. More specifically, resistance to soluble CEA antigen could be found only for IgG1 antibodies, the variable regions of which comprised the amino acid sequence “DRGLRFYFDY” of the CDR-H3 of murine monoclonal antibody A5B7 (Chester, loc. cit.; Harwood, Br J Cancer. 54 (1986), 75-82).

As set forth above, many therapeutic approaches directed against CEA-bearing epithelial tumors in humans are seriously hampered by the presence of high levels of soluble CEA antigen in the plasma of cancer patients. Soluble CEA antigen—frequently present in high concentrations in the serum of cancer patients with progressive tumors, recurrent cancer, metastasic tumors, high tumor load/burden, or late-stage tumors, blocks the therapeutics directed against CEA-positive tumor cells, thus preventing tumor cell recognition and destruction. Therefore, the actual amount of the therapeutic which reaches the tumor is reduced, resulting in a reduced low or even no anti-tumor activity. This limitation so far restricts e.g. antibody-based approaches to those patients with very low serum levels of soluble CEA antigen unlikely to prevent therapeutic-tumor cell interaction. Current therapeutic approaches with CEA specific Ig molecules do not show anti-tumor activity in patients with high serum levels of soluble CEA.

In the present invention, it has been found that it is possible to generate antibody-therapeutics with specificity for human CEA, wherein the cytotoxic (ADCC) activity directed against tumor cells is resistant to even high concentrations of soluble CEA antigen. This finding is entirely unexpected in view of the fact that the IgG1 antibodies of the invention bind to soluble CEA antigen (see Example 5). Nevertheless, the IgG1 antibodies as defined herein are resistant to the presence of even high levels of soluble CEA in their cytotoxic activity towards tumor cells. Thus, the present invention provides means and methods particularly suited for the treatment of tumor patients with high soluble CEA concentrations in their plasma, as observed e.g. during tumor progression, for recurrent cancer, for metastasis, for patients with high tumor load/burden, or late-stage tumors.

In light of this finding, the IgG1 antibodies in the pharmaceutical compositions of the invention in the following are referred to as being resistant to soluble CEA antigen. The term “resistance to soluble CEA antigen”, “resistant to soluble CEA” (or related terms) as used herein refers to the fact that the cytotoxicity against CEA-positive tumor cells mediated by said IgG1 antibodies is not affected by increasing concentrations of soluble CEA. In particular, the cytotoxic activity is not inhibited by even high concentrations of soluble CEA. As set forth above, CEA levels in the blood of healthy individuals is less than 2 ng/ml. High soluble CEA concentrations in the serum/plasma of tumor patients are characteristic for progressive, recurrent, metastatic, or late stage tumors and for patients with high tumor load. Thus, the present invention provides means and methods particularly suited for the treatment of epithelial tumor patients with such high soluble CEA concentrations in their plasma. The term “high soluble CEA concentrations” as used herein denotes a soluble serum/plasma-CEA concentration higher than 10, 20, 50, 70, 80, 90 or 100 ng/ml. The serum/plasma CEA concentration may, inter alia, be determined by ELISA techniques. Preferably, said soluble serum/plasma-CEA concentration is higher than 100 ng/ml, as for example determined by ELISA. The CEA serum concentration can be determined e.g. by CEA ELISA assays (see e.g. IBL CEA EIA, IBL Hamburg, Germany).

In accordance with this invention, the term “pharmaceutical composition” relates to a composition for administration to a human patient. Preferably, the pharmaceutical composition comprises suitable formulations of carriers, stabilizers and/or excipients. In a preferred embodiment, the pharmaceutical composition comprises a composition for parenteral, transdermal, intraluminal, intraarterial, intrathecal and/or intranasal administration or by direct injection into tissue. It is in particular envisaged that said composition is administered to a patient via infusion or injection. Administration of the suitable compositions may be effected by different ways, e.g., by intravenous, intraperitoneal, subcutaneous, intramuscular, topical or intradermal administration. The composition of the present invention may further comprise a pharmaceutically acceptable carrier. Examples of suitable pharmaceutical carriers are well known in the art and include phosphate buffered saline solutions, water, various types of wetting agents, sterile solutions, liposomes, etc. Compositions comprising such carriers can be formulated by well known conventional methods. These compositions can be administered to the subject at a suitable dose which can be determined e.g. by dose escalating studies by administration of increasing doses of the IgG1 antibodies exhibiting resistance to soluble serum CEA antigen described herein. As set forth above, the IgG1 antibodies described herein with resistance to soluble serum CEA antigen can be advantageously used in the treatment of cancer patients with high CEA serum concentrations, such as progressive tumors, recurrent cancer, metastatic tumors, high tumor load/burden, or late stage tumors. These compositions can also be administered in combination with other proteinaceous and non-proteinaceous drugs, e.g. in the form of a co-therapy. These drugs may be administered simultaneously with the composition comprising the IgG1 antibodies as defined herein or separately before or after administration of said IgG1 antibodies in timely defined intervals and doses. The dosage regimen will be determined by the attending physician and clinical factors. As is well known in the medical arts, dosages for any one patient depend upon many factors, including the patient's size, body surface area, age, the particular compound to be administered, sex, time and route of administration, general health, and other drugs being administered concurrently. Preparations for parenteral administration include sterile aqueous or non-aqueous solutions, and suspensions. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oils, and injectable organic esters such as ethyl oleate. Aqueous carriers include water, aqueous solutions, or suspensions, including saline and buffered media. Parenteral vehicles include sodium chloride solution, Ringer's dextrose, dextrose and sodium chloride, or lactated Ringer's. Intravenous vehicles include fluid and nutrient replenishers, electrolyte replenishers (such as those based on Ringer's dextrose), and the like. Preservatives and other additives may also be present such as, for example, antimicrobials, anti-oxidants, chelating agents, inert gases and the like. In addition, the composition of the present invention might comprise proteinaceous carriers, like, e.g., serum albumin or immunoglobulin, preferably of human origin. It is envisaged that the co-therapy comprise, in addition to the IgG1 antibodies as defined herein, further biologically active agents, depending on the intended use of the composition. Such agents might be drugs acting on the gastro-intestinal system, drugs acting as antineoplastic agents, chemotherapeutics, cytostatica, drugs preventing hyperurikemia, drugs inhibiting immunoreactions (e.g. corticosteroids), drugs modulating the inflammatory response, drugs acting on the circulatory system and/or agents such as cytokines known in the art.

Preferably, the IgG1 antibody as defined herein is formulated in a buffer, a stabilizer and a surfactant. The buffer may be a phosphate, citrate, succinate or acetate buffer. The stabilizer may be (an) amino acid(s) and/or a sugar. The surfactants may be detergents, PEGs, or the like. More preferably, the IgG1 antibody as defined herein is formulated in citrate, lysine, trehalose and Tween 80. As a diluent for the pharmaceutical composition of the invention, isotonic saline and Tween 80 is preferred.

As used herein, an “antibody” denotes immunoglobulin molecules, i.e., molecules that contain an antigen binding site that immunospecifically binds an antigen, preferably human CEA. All antibodies are constructed in the same way. They form paired heavy and light polypeptide chains, and the generic term immunoglobulin is used for all such proteins. Within this general category, however, five different classes of immunoglobulins—IgM, IgD, IgG, IgA, and IgE—can be distinguished by their C regions. IgG antibodies are large molecules, having a molecular weight of approximately 150 kDa, composed of two different kinds of polypeptide chain. One, of approximately 50 kDa, is termed the heavy or H chain, and the other, of 25 kDa, is termed the light or L chain. Each IgG molecule consists of two heavy chains and two light chains. The two heavy chains are linked to each other by disulfide bonds and each heavy chain is linked to a light chain by a disulfide bond. In any given immunoglobulin molecule, the two heavy chains and the two light chains are identical, giving an antibody molecule two identical antigen-binding sites, and thus the ability to bind simultaneously to two identical structures. Two types of light chain, termed lambda and kappa, are found in antibodies. A given immunoglobulin either has lambda chains or kappa chains, never one of each. No functional difference has been found between antibodies having lambda or kappa light chains, and either type of light chain may be found in antibodies of any of the five major classes. The ratio of the two types of light chain varies from species to species. In mice, the average kappa to lambda ratio is 20:1, whereas in humans it is 2:1 and in cattle it is 1:20. The reason for this variation is unknown. By contrast, the class, and thus the effector function of an antibody, is defined by the structure of its heavy chain. There are five main heavy-chain classes or isotypes, some of which have several subtypes, and these determine the functional activity of an antibody molecule. The five major classes of immunoglobulin are immunoglobulin M (IgM), immunoglobulin D (IgD), immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin E (IgE). Their heavy chains are denoted by the corresponding lower-case Greek letter (mu, delta, gamma, alpha, and epsilon, respectively). IgG is by far the most abundant immunoglobulin and has several subclasses (IgG1, 2, 3, and 4 in humans). Their distinctive functional properties are conferred by the carboxy-terminal part of the heavy chain, where it is not associated with the light chain. The general structural features of all the isotypes are similar. The structure of an IgG antibody, the most abundant isotype in plasma, as a typical antibody molecule is exemplified in FIG. 1.

Preferably, the antibodies as defined herein are IgG antibodies. As is well known in the art, an IgG comprises not only the variable antibody regions responsible for the highly discriminative antigen recognition and binding, but also the constant regions of the heavy and light antibody polypeptide chains normally present in endogenously produced antibodies and, in some cases, even decoration at one or more sites with carbohydrates. Such glycosylation is generally a hallmark of the IgG format, and portions of these constant regions make up the so called Fc region of a full antibody which is known to elicit various effector functions in vivo, such as e.g. antibody-dependent cellular cytotoxicity (ADCC). In addition, the Fc region mediates binding of the IgG to an Fc receptor, hence prolonging half life in vivo as well as facilitating homing of the IgG to locations with increased Fc receptor presence. Advantageously, the IgG antibody is an IgG1 antibody specifically binding to the human CEA antigen, formats which are preferred since their mechanism of action in vivo is particularly well understood and characterized. This is especially the case for IgG1 antibodies.

The IgG1 antibodies referred to herein comprise the variable region(s) as defined above in combination with the entirety or a portion of the hinge region, CH1, CH2, and CH3 domains and CL domains; see e.g. FIG. 1. Generally, in a variable region, a VH domain is paired with a VL domain to provide an antibody antigen binding site. Preferably, the VH domain comprising (i) a CDR-H1 having the amino acid sequence “SYWMH” (SEQ ID NO. 29) and a CDR-H2 having the amino acid sequence “FIRNKANGGTTEYAASVKG” (SEQ ID NO. 28) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7 or (ii) a CDR-H1 having the amino acid sequence “TYAMH” (SEQ ID NO. 31) and a CDR-H2 having the amino acid sequence “LISNDGSNKYYADSVKG” (SEQ ID NO. 30) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7 is paired with the VL domain comprising a CDR-L1 having the amino acid sequence “TLRRGINVGAYSIY” (SEQ ID NO. 34) and a CDR-L2 having the amino acid sequence “YKSDSDKQQGS” (SEQ ID NO. 33) and a CDR-L3 having the amino acid sequence “MIWHSGASAV” (SEQ ID NO. 32), so that an antibody antigen binding site is formed comprising one of the mentioned VH domains and the said VL domain. The anti-CEA IgG1 antibodies defined herein may be rodent antibodies (i.e. from mice or rats). Preferably, said IgG1 antibodies are humanized antibodies as set forth in more detail below.

According to the present invention, the term “binding domain” or “variable region” used in the context with Ig-derived antigen-interaction comprises fragments and derivatives of polypeptides which at least comprise one CDR derived from an antibody, antibody fragment or derivative thereof. It is envisaged by the invention, that the binding domain specifically binding to human CEA of the IgG1 antibody defined herein comprises at least one CDR, preferably a CDR-H3, more preferably the CDR-H3 of murine monoclonal antibody A5B7 with the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of A5B7. As shown in the following Examples, the cytotoxic activity against tumor cells of the IgG1 antibodies defined herein comprising said mAb A5B7-derived CDR-H3 “DRGLRFYFDY” (SEQ ID NO. 27) amino acid sequence is resistant to soluble CEA antigen, thereby allowing the treatment of tumor patients with high serum CEA concentrations in their plasma.

As used herein, “human” refers to the species Homo sapiens. A “human” molecule, e.g. human CEA, is therefore the variant of that molecule as it is naturally expressed in Homo sapiens.

The term “epithelial tumor” as used herein denotes a tumor of epithelial origin which is CEA positive (Cancer Medicine; 6th ed.; Kufe, Donald W.; Pollock, Raphael E.; Weichselbaum, Ralph R.; Bast, Robert C., Jr.; Gansler, Ted S.; Holland, James F.; Frei III, Emil, editors. Hamilton (Canada): BC Decker Inc. 2003; http://www.dkfz.de; http://www.krebsinformationsdienst.de/Krebsarten/index.html). The epithelial tumor to be treated may be a gastrointestinal adenocarcinoma, a breast adenocarcinoma or a lung adenocarcinoma. Said gastrointestinal adenocarcinoma is preferably a colorectal, pancreatic, an oesophageal or a gastric adenocarcinoma. As set forth herein, the pharmaceutical composition of the invention is particularly advantageous for the treatment of patients with progressive tumors, metastasis, recurrent cancer, late stage epithelial tumors, high epithelial tumor load/tumor burden, or tumor patients with a CEA serum concentration higher than 100 ng/ml (as determined e.g. by ELISA), characterized by high levels of soluble CEA antigen in the serum/plasma of the tumor patients. It is also within the scope of the invention that said pharmaceutical composition be administered after surgical removal of the primary tumor. For example, disseminated residual tumor cells derived from a CEA producing epithelial tumor also shed CEA into their microenvironments, in the surrounding of which the level of soluble CEA is high. Accordingly, resistance to soluble CEA of cytotoxic activity of IgG1 antibodies as defined herein is advantageous also for the treatment of minimal residual disease. Thus, it is envisaged that the IgG1 antibodies as defined herein may be administered in a period in which serum CEA levels decrease (due to the removal of the CEA source, i.e. the primary tumor) in order to kill remaining tumor cells. Or the IgG1 antibodies as defined herein may be useful after the removal of the primary tumor, in the case that serum CEA levels increase due to the formation of secondary tumors or metastasis. The CEA serum concentration can be determined e.g. by CEA ELISA assays (see e.g. IBL CEA EIA, IBL Hamburg, Germany). As set forth above, in many antibody-based therapeutic approaches, said serum CEA inhibits binding of the antibody to membrane-bound CEA on the tumor cells and blocks the activity of antibody, thereby worsening the success of the anti-tumor therapy.

As used herein, the term “specifically binds” or related expressions such as “specifically binding” or “specific reactivity with/to” etc. refer to the ability of the binding domains of the IgG1 antibody as defined herein to discriminate between a first and/or second molecule to such an extent that, from a pool of a plurality of different molecules as potential binding partners, only said respective first and/or second molecule is/are bound, or is/are significantly bound. Such binding measurements can be routinely performed e.g. on a Biacore apparatus, by ELISA, FACS analysis or the like. More specifically, the binding domain of the IgG1 antibody as defined herein binds to a epithelial tumor antigen, i.e. human CEA (carcinoembryonic antigen, carcinoembryonic antigen-related cell adhesion molecule 5; CEACAM5; CD66e), as set forth below. The term “specifically binding” means in accordance with this invention that the IgG1 antibody molecule is capable of specifically interacting with and/or binding to at least two, three, four, five, six, seven, eight or even more amino acids of human CEA as defined herein. Said term relates to the specificity of the antibody molecule, i.e. to its ability to discriminate between the specific regions of the human CEA antigen as defined herein. The specific interaction of the antigen-interaction-site with its specific antigen may result in an initiation of a signal, e.g. due to the induction of a change of the conformation of the antigen, an oligomerization of the antigen, etc. Further, said binding may be exemplified by the specificity of a “key-lock-principle”. Thus, specific motifs in the amino acid sequence of the antigen-interaction-site and the antigen bind to each other as a result of their primary, secondary or tertiary structure as well as the result of secondary modifications of said structure. The specific interaction of the antigen-interaction-site with its specific antigen may result as well in a binding of said site to the antigen.

The “specific binding” of an antibody is characterized primarily by two parameters: a qualitative parameter (the binding epitope, or where the antibody binds) and a quantitative parameter (the binding affinity, or how strongly it binds where it does). Which epitope is bound by an antibody can advantageously be determined by e.g. known FACS methodology, peptide-spot epitope mapping, mass spectroscopy or peptide ELISA. The strength of antibody binding to a particular epitope may be advantageously be determined by e.g. known Biacore and/or ELISA methodologies. A combination of such techniques allows the calculation of a signal:noise ratio as a representative measure of binding specificity. In such a signal:noise ratio, the signal represents the strength of antibody binding to the epitope of interest, whereas the noise represents the strength of antibody binding to other, non-related epitopes differing from the epitope of interest. Preferably, a signal:noise ratio for an epitope of interest which is about 50-fold higher than for other epitopes different from the epitope of interest may be taken as an indication that the antibody evaluated binds the epitope of interest in a specific manner, i.e. is a “specific binder”.

The term “specific binding” or “specific interaction” as used in accordance with the present invention means that the IgG1 antibody construct does not or essentially does not cross-react with polypeptides of similar structures. Cross-reactivity of a panel of antibody constructs under investigation may be tested, for example, by assessing binding of said panel of antibody constructs under conventional conditions (see, e.g., Harlow and Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, 1988 and Using Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, 1999) to the polypeptide of interest as well as to a number of more or less (structurally and/or functionally) closely related polypeptides. For example, it is within the scope of the invention that the binding domain of the IgG1 antibody defined herein binds to human CEA (carcinoembryonic antigen; CEACAM5; CEA; CD66e), i.e. both to soluble CEA and to membrane-bound CEA, whereas IgG1 antibodies binding to other CEA family members, such as biliary glycoprotein (CEACAM1; BGP1; TM-CEA; CD66a), are excluded from said scope.

Examples for the specific interaction of an antigen-interaction-site with a specific antigen comprise the specificity of a ligand for its receptor. Said definition particularly comprises the interaction of ligands which induce a signal upon binding to its specific receptor. Examples for corresponding ligands comprise cytokines which interact/bind with/to its specific cytokine-receptors. Also particularly comprised by said definition is the binding of an antigen-interaction-site to antigens like antigens of the selectin family, integrins and of the family of growth factors like EGF. Another example for said interaction, which is also particularly comprised by said definition, is the interaction of an antigenic determinant (epitope) with the antigenic binding site of an antibody.

The term “binding to/interacting with” may also relate to a conformational epitope, a structural epitope or a discontinuous epitope consisting of two regions of the human target molecule, i.e. human CEA, or parts thereof. In context of this invention, a conformational epitope is defined by two or more discrete amino acid sequences separated in the primary sequence which come together on the surface of the molecule when the polypeptide folds to the native protein (Sela, (1969) Science 166, 1365 and Layer, (1990) Cell 61, 553-6).

The term “discontinuous epitope” means in context of the invention non-linear epitopes that are assembled from residues from distant portions of the polypeptide chain. These residues come together on the surface of the molecule when the polypeptide chain folds into a three-dimensional structure to constitute a conformational/structural epitope.

“CEA” denotes the carcinoembryonic antigen (carcinoembryonic antigen-related cell adhesion molecule 5; CEACAM5; CEA; CD66e), an antigen expressed in a large number of tumors of epithelial origin (Hammarström, Sem. Cancer Biol. 9 (1999), 67-81; Shively and Beatty CRC Crit. Rev. Oncol. Hematol. 2 (1985), 355-399). The amino acid sequence of human CEA is depicted in GenBank accession number NM_(—)004363 and comprises SEQ ID NO. 37.

In the present invention, it has been surprisingly found that it is possible to generate antibody-based therapeutics with specificity for human CEA, wherein the cytotoxic activity (ADCC) directed against tumor cells is resistant to even high concentrations of soluble CEA antigen. This finding is entirely unexpected in view of the fact that the IgG1 antibodies defined herein bind to soluble CEA antigen. For example, when IgG1 antibody constructs derived from monoclonal antibody T84.66 have been generated, these antibodies were highly sensitive to soluble CEA antigen, ie. their cytotoxic activity (ADCC) has been blocked in the presence of soluble CEA antigen. These constructs have also been found to be capable of binding to soluble CEA. In view of this, it was concluded that soluble CEA antigen prevents the antibodies from exerting their cytotoxic activity. In contrast, the IgG1 antibodies as defined herein are resistant to the presence of even high levels of soluble CEA in their cytotoxic activity towards tumor cells. Even more surprising, it has been found that the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7 is sufficient to mediate resistance to soluble CEA antigen when used in a human CEA-binding domain (i.e. human binding domains specifically binding to human CEA) of human IgG1 antibodies. Due to their human origin (with exception of the “DRGLRFYFDY” amino acid sequence), said constructs are low or non-immunogenic when being administered to human tumor patients. In summary, the pharmaceutical compositions comprising the IgG1 antibodies as defined herein are particularly useful for the treatment of epithelial tumor patients with high soluble CEA concentrations in their plasma, as observed e.g. during tumor progression, for recurrent cancer, for metastasis, for patients with high tumor load/burden, or late-stage tumors. Such IgG1 antibodies as defined herein can be generated by methods described in the art, e.g. by phage-display based techniques; see also the following Examples.

It is preferred that the binding domain specifically binding to human CEA of the IgG1 antibody defined herein comprises at least one CDR, preferably a CDR-H3, more preferably a part of or the complete CDR-H3 of murine monoclonal antibody A5B7 with the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95 (“D”, Aspartic acid), 96 (“R”; Arginine), 97 (“G”; Glycine), 98 (“L”; Leucine), 99 (“R”; Arginine), 100 (“F”; Phenylalanine), 100a (“Y”; Tyrosine), 100b (“F”; Phenylalanine), 101 (“D”; Aspartic acid), and 102 (“Y”; Tyrosine), respectively. Numbering according to the Kabat system is set forth e.g. in Kabat, E. A., T. T. Wu, H. M. Perry, K. S. Gottesman, and C. Foeller. 1991. Sequences of Proteins of Immunological Interest, 5th ed. Bethesda, Md.: National Center for Biotechnology Information, National Library of Medicine.

As shown in the following Examples, the cytotoxic activity (ADCC) against tumor cells of the IgG1 antibodies defined herein comprising said mAb A5B7-derived CDR-H3 “DRGLRFYFDY” (SEQ ID NO. 27) amino acid sequence in the binding domain interacting with CEA are resistant to soluble CEA antigen, thereby allowing the treatment of tumor patients with high serum CEA concentrations in their plasma. It may be desirable to further modify this A5B7-derived “DRGLRFYFDY” CDR-H3 amino acid sequence e.g. in order to improve affinity for the CEA target antigen (on the epithelial tumor cells) and/or to optimize the “fine specificity” of the IgG1 antibodies as defined herein. To this end, for example, in the amino acid sequence “DX₁X₂X₃X₄FYFDY”, various amino acid residues may be tested at positions “X₁”, “X₂”, “X₃” and/or “X₄” (corresponding to Kabat positions 96 (“X₁”), 97 (“X₂”), 98 (“X₃”) and 99 (“X₄”), respectively, of CDR-H3 of murine monoclonal antibody A5B7) in order to identify a modified CDR-H3 with improved affinity and/or fine specificity. For instance, “X₁”, “X₂”, “X₃” or “X₄” may represent amino acid residue “R” (Arginine), “G” (Glycine), “L” (Leucine), “Y” (Tyrosine), “A” (Alanine), “D” (Aspartic acid), “S” (Serine), “W” (Tryptophan), “F” (Phenylalanine) or “T” (Threonine). Herein, one, two, three or all four of the indicated “X” positions may be exchanged in comparison to the original “RGLR” amino acid sequence at Kabat positions 96 to 99 in the CDR-H3 “DRGLRFYFDY” (SEQ ID NO. 27) amino acid sequence. However, it is excluded from the scope of the claims of the invention that “X₁”, “X₂”, “X₃” and “X₄” represent the same amino acid, e.g. that “X₁”, “X₂”, “X₃” and “X₄” are all “F” (Phenylalanine). The above-mentioned modification of the A5B7-derived “DRGLRFYFDY” CDR-H3 amino acid sequence can be achieved by methods known in the art, such as PCR using randomized primers, which allows the generation of IgG1 antibodies with such modified CDR-H3 regions in the CEA-binding domain. Affinity or fine specificity of these modified IgG1 antibodies can be tested by methods described in the art, e.g. by ELISA, Biacore or FACS analysis. The resistance to soluble CEA antigen of an IgG1 antibody with such a modified CDR-H3 can be tested in cytotoxicity (antibody dependent cell-mediated cytotoxicity, ADCC) assays in the presence of increasing amounts of soluble CEA, as described in the following Examples.

Preferably, the variable region of the IgG1 antibodies defined herein comprises at least the amino acid sequences selected from the group consisting of:

(a) a CDR-H1 having the amino acid sequence “SYWMH” (SEQ ID NO. 29) and a CDR-H2 having the amino acid sequence “FIRNKANGGTTEYAASVKG” (SEQ ID NO. 28) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7; and (b) a CDR-H1 having the amino acid sequence “TYAMH” (SEQ ID NO. 31) and a CDR-H2 having the amino acid sequence “LISNDGSNKYYADSVKG” (SEQ ID NO. 30) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7.

More preferably, said variable region comprises a CDR-L1 having the amino acid sequence “TLRRGINVGAYSIY” (SEQ ID NO. 34) and/or a CDR-L2 having the amino acid sequence “YKSDSDKQQGS” (SEQ ID NO. 33) and/or a CDR-L3 having the amino acid sequence “MIWHSGASAV” (SEQ ID NO. 32).

The amino acid sequence of the VH region of the binding domain specific for human CEA of the IgG1 antibodies defined herein is preferably SEQ ID NO. 20, 22 or 24.

The amino acid sequence of the VL region of the binding domain specific for human CEA of the IgG1 antibodies defined herein is preferably SEQ ID NO. 26.

Even more preferred, the variable (V) regions of the binding domain specific for CEA of the IgG1 antibodies defined herein are selected from the group consisting of:

(a) the VH region consists of the amino acid sequence shown in SEQ ID NO. 22 and the VL region consists of the amino acid sequence shown in SEQ ID NO. 26; (b) the VH region consists of the amino acid sequence shown in SEQ ID NO. 20 and the VL region consists of the amino acid sequence shown in SEQ ID NO. 26; and (c) the VH region consists of the amino acid sequence shown in SEQ ID NO. 24 and the VL region consists of the amino acid sequence shown in SEQ ID NO. 26.

Most preferred, said IgG1 antibody as defined herein comprises an amino acid sequence selected from the group consisting of:

-   -   (a) an amino acid sequence of the heavy chain shown in SEQ ID         NO. 77 and an amino acid sequence of the light chain shown in         SEQ ID NO. 80;     -   (b) an amino acid sequence of the heavy chain shown in SEQ ID         NO. 78 and an amino acid sequence of the light chain shown in         SEQ ID NO. 80;     -   (c) an amino acid sequence of the heavy chain shown in SEQ ID         NO. 79 and an amino acid sequence of the light chain shown in         SEQ ID NO. 80; and     -   (d) an amino acid sequence at least 85% identical, more         preferred at least 90% identical, most preferred at least 95%         identical to the amino acid sequence of (a), (b) or (c).

Most preferably and as documented in the appended examples, the “IgG1 antibody” to be employed in the pharmaceutical composition of the invention is a humanized IgG1 antibody with human constant regions and a humanized variable region comprising the amino acid sequence “DRGLRFYFDY” corresponding to Kabat positions 95-102 (SEQ ID NO. 27) of the CDR-H3 of murine monoclonal antibody A5B7.

Preferably, the light chain constant region of said IgG1 antibody is a lambda light chain constant region, preferably a human lambda light chain constant region.

The IgG1 antibody as defined herein may be derivatized, for example with an organic polymer, e.g. with one or more molecules of polyethylene glycol (“PEG”) and/or polyvinyl pyrrolidone (“PVP”). As is known in the art, such derivatization can be advantageous in modulating the pharmacodynamic properties of antibodies or fragments thereof. Especially preferred are PEG molecules derivatized as PEG-maleimide, enabling conjugation with the antibody or fragment thereof in a site-specific manner via the sulfhydryl group of a cysteine amino acid. Of these, especially preferred are 20 kD and/or 40 kD PEG-maleimide, in either branched or straight-chain form.

Moreover, the IgG1 antibody as defined herein may be fused to radionuclides (e.g. ¹³¹I), cell toxins (e.g. Pseudomonas toxin A) or cytokines, such as IL-2. The resulting fusion proteins are preferably used for therapeutic purposes in the treatment of epithelial tumors. Antibodies of the invention fused to radionuclides may also be useful e.g. for diagnostic purposes.

In another preferred embodiment of the pharmaceutical composition of the invention, said epithelial tumor to be treated is a gastrointestinal adenocarcinoma, a breast adenocarcinoma or a lung adenocarcinoma. Said gastrointestinal adenocarcinoma is preferably a colorectal, pancreatic, an oesophageal or a gastric adenocarcinoma.

More preferably, said pharmaceutical composition of the invention is for the treatment of progressive tumors, late stage tumors, tumor patients with high tumor load/burden, metastatic tumors, or tumor patients with a CEA serum concentration higher than 100 ng/ml. Said CEA serum concentration may be determined e.g. by ELISA.

In a further preferred embodiment of the pharmaceutical composition of the invention, the IgG1 antibodies defined herein are humanized and/or deimmunized.

As used herein, the term “CDR-grafted”, “humanized” or “humanization” are used interchangeably to refer to a human IgG1 antibody comprising in its binding domains at least one complementarity determining region (“CDR”) from a non-human antibody or fragment thereof. Humanization approaches are described for example in WO 91/09968 and U.S. Pat. No. 6,407,213. As non-limiting examples, the term encompasses the case in which a variable region of the binding domain comprises a single CDR region, for example the third CDR region (CDR-H3) of the VH, from another non-human animal, for example a rodent, as well as the case in which a or both variable region/s comprise at each of their respective first, second and third CDRs the CDRs from said non-human animal. In the event that all CDRs of a binding domain of the antibody have been replaced by their corresponding equivalents from, for example, a rodent, one typically speaks of “CDR-grafting”, and this term is to be understood as being encompassed by the term “humanized” as used herein. The term “humanized” also encompasses cases in which, in addition to replacement of one or more CDR regions within a VH and/or VL of the binding domain further mutation/s (e.g. substitutions) of at least one single amino acid residue/s within the framework (“FR”) regions between the CDRs has/have been effected such that the amino acids at that/those positions correspond/s to the amino acid/s at that/those position/s in the animal from which the CDR regions used for replacement is/are derived. As is known in the art, such individual mutations are often made in the framework regions following CDR-grafting in order to restore the original binding affinity of the non-human antibody used as a CDR-donor for its target molecule. The term “humanized” may further encompass (an) amino acid substitution(s) in the CDR regions from a non-human animal to the amino acid(s) of a corresponding CDR region from a human antibody, in addition to the amino acid substitutions in the framework regions as described above.

More specifically, as used herein, “humanized antibodies” or related terms encompass IgG1 antibodies having the amino acid sequence of a human immunoglobulin with a variable region comprising human CDR- and framework region-sequences, with exception of a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7. Such antibodies can be generated as set forth in the following Examples. It is especially advantageous that the IgG1 antibody as described herein be a humanized antibody. In contemplating an antibody agent intended for therapeutic administration to humans, it is highly advantageous that the major part of this antibody is of human origin. Following administration to a human patient, a humanized antibody (or fragment) thereof will most probably not elicit a strong immunogenic response by the patient's immune system, i.e. will not be recognized as being a “foreign”, that is non-human protein. This means that no host, i.e. patient antibodies will be generated against the therapeutic antibody which would otherwise block the therapeutic antibody's activity and/or accelerate the therapeutic antibody's elimination from the body of the patient, thus preventing it from exerting its desired therapeutic effect. The term “humanized” antibody as used herein is to be understood as meaning that the IgG1 antibody as defined herein comprises (an) amino acid sequence(s) contained in the human antibody repertoire, and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7. For the purposes of definition herein, an antibody, or its fragment, may therefore be considered humanized if it consists of such (a) human amino acid sequence(s), i.e. if the amino acid sequence(s) of the antibody in question or fragment thereof is (are) identical to (an) expressed human germline amino acid sequence(s), with exception of the murine CDR-H3 indicated above. An IgG1 antibody as defined herein may also be regarded as humanized if it consists of (a) sequence(s) that deviate(s) from its (their) closest human germline sequence(s) by no more than would be expected due to the imprint of somatic hypermutation. Preferably, the (humanized) IgG1 antibodies as defined herein have a human constant region and a human variable region comprising a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7. As set forth above, said CDR-H3 mediates resistance to soluble CEA.

As used herein, the term “deimmunized” or “deimmunization” denotes modification of the binding domain vis-à-vis an original wild type construct by rendering said wild type construct non-immunogenic or less immunogenic in humans. Deimmunization approaches are shown e.g. in WO 00/34317, WO 98/52976, WO 02/079415 or WO 92/10755. The term “deimmunized” also relates to constructs, which show reduced propensity to generate T cell epitopes. In accordance with this invention, the term “reduced propensity to generate T cell epitopes” relates to the removal of T-cell epitopes leading to specific T-cell activation. Furthermore, “reduced propensity to generate T cell epitopes” means substitution of amino acids contributing to the formation of T cell epitopes, i.e. substitution of amino acids, which are essential for formation of a T cell epitope. In other words, “reduced propensity to generate T cell epitopes” relates to reduced immunogenicity or reduced capacity to induce antigen independent T cell proliferation. The term “T cell epitope” relates to short peptide sequences which can be released during the degradation of peptides, polypeptides or proteins within cells and subsequently be presented by molecules of the major histocompatibility complex (MHC) in order to trigger the activation of T cells; see inter alia WO 02/066514. For peptides presented by MHC class II such activation of T cells can then give rise to an antibody response by direct stimulation of T cells to produce said antibodies. “Reduced propensity to generate T-cell epitopes” and/or “deimmunization” may be measured by techniques known in the art. Preferably, de-immunization of proteins may be tested in vitro by T cell proliferation assay. In this assay PBMCs from donors representing >80% of HLA-DR alleles in the world are screened for proliferation in response to either wild type or de-immunized peptides. Ideally cell proliferation is only detected upon loading of the antigen-presenting cells with wild type peptides. Alternatively, one may test deimmunization by expressing HLA-DR tetramers representing all haplotypes. These tetramers may be tested for peptide binding or loaded with peptides substitute for antigen-presenting cells in proliferation assays. In order to test whether deimmunized peptides are presented on HLA-DR haplotypes, binding of e.g. fluorescence-labeled peptides on PBMCs can be measured. Furthermore, deimmunization can be proven by determining whether antibodies against the deimmunized molecules have been formed after administration in patients. Preferably, antibody derived molecules are deimmunized in the framework regions and most of the CDR regions are not modified in order to generate reduced propensity to induce T cell epitope so that the binding affinity of the CDR regions is not affected. Even elimination of one T cell epitope results in reduced immunogenicity. In summary, the above approaches help to reduce the immunogenicity of the therapeutic IgG1 antibodies as defined herein when being administered to epithelial tumor patients.

In another aspect, the invention relates to an IgG1 antibody comprising an amino acid sequence selected from the group consisting of:

-   -   (a) an amino acid sequence of the heavy chain shown in SEQ ID         NO. 77 and an amino acid sequence of the light chain shown in         SEQ ID NO. 80;     -   (b) an amino acid sequence of the heavy chain shown in SEQ ID         NO. 78 and an amino acid sequence of the light chain shown in         SEQ ID NO. 80;     -   (c) an amino acid sequence of the heavy chain shown in SEQ ID         NO. 79 and an amino acid sequence of the light chain shown in         SEQ ID NO. 80; and     -   (d) an amino acid sequence at least 85% identical, more         preferred at least 90% identical, most preferred at least 95%         identical to the amino acid sequence of (a), (b) or (c).

The invention also relates to nucleic acids encoding the IgG1 antibodies as defined above. Advantageously, said IgG1 antibodies as defined herein or nucleic acids encoding the same are used as pharmaceutical compositions for the treatment of (an) epithelial tumor(s) in human. Said epithelial tumor(s) is (are) CEA-positive. The cytotoxic activity against CEA-positive epithelial tumor cells of the IgG1 antibodies in these pharmaceutical compositions of the invention is resistant to even high concentrations of soluble CEA antigen in the plasma of tumor patients.

Whether any particular polypeptide is at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identical to a nucleotide or amino acid sequence defined herein can be determined conventionally using known computer programs. A preferred method for determining the best overall match between a query sequence (a sequence defined herein) and a subject sequence, also referred to as a global sequence alignment, can be determined using the FASTDB computer program based on the algorithm of Brutlag et al. (Comp. App. Biosci. 6:237-245 (1990)). In a sequence alignment the query and subject sequences are both DNA sequences. An RNA sequence can be compared by converting U's to T's.

The invention also provides for a pharmaceutical composition comprising a nucleic acid sequence encoding an IgG1 antibody as defined herein. Said nucleic acid can be utilized e.g. for gene therapy approaches in order to treat an epithelial tumor in a human, as set forth in more detail below.

The invention further relates to a pharmaceutical composition comprising a vector which comprises a nucleic acid sequence as defined above. Preferably, said vector further comprises a regulatory sequence which is operably linked to said nucleic acid sequence defined above. More preferably, said vector is an expression vector. It is also envisaged that e.g. one expression vector encodes the heavy chains of said antibody, whereas another expression vector codes for the light chains.

Furthermore, the vector of the present invention may also be a gene transfer or gene targeting vector. Gene therapy, which is based on introducing therapeutic genes or nucleic acids into cells by ex-vivo or in-vivo techniques is one of the most important applications of gene transfer. Suitable vectors, methods or gene-delivering systems for in-vitro or in-vivo gene therapy are described in the literature and are known to the person skilled in the art; see, e.g., Giordano, Nature Medicine 2 (1996), 534-539; Schaper, Circ. Res. 79 (1996), 911-919; Anderson, Science 256 (1992), 808-813, Isner, Lancet 348 (1996), 370-374; Muhlhauser, Circ. Res. 77 (1995), 1077-1086; Onodua, Blood 91 (1998), 30-36; Verzeletti, Hum. Gene Ther. 9 (1998), 2243-2251; Verma, Nature 389 (1997), 239-242; Anderson, Nature 392 (Supp. 1998), 25-30; Wang, Gene Therapy 4 (1997), 393-400; Wang, Nature Medicine 2 (1996), 714-716; WO 94/29469; WO 97/00957; U.S. Pat. No. 5,580,859; U.S. Pat. No. 5,589,466; U.S. Pat. No. 4,394,448 or Schaper, Current Opinion in Biotechnology 7 (1996), 635-640, and references cited therein. The nucleic acid molecules and vectors as defined herein may be designed for direct introduction or for introduction via liposomes, viral vectors (e.g. adenoviral, retroviral), electroporation, or other delivery systems into the cell. Additionally, a baculoviral system can be used as eukaryotic expression system for the nucleic acid molecules as defined herein. The introduction and gene therapeutic approach should, preferably, lead to the expression of a functional IgG1 antibody construct as defined herein, whereby said IgG1 antibody construct is particularly useful in the treatment, amelioration and/or prevention of an epithelial tumor in a human.

In a further aspect, the invention relates to a pharmaceutical composition comprising a host transformed or transfected with a vector or a nucleic acid as defined above.

Preferably, the pharmaceutical composition further comprises suitable formulations of carriers, stabilizers and/or excipients.

In another aspect, the invention relates to a process for the production of a pharmaceutical composition as defined above, said process comprising culturing a host as defined above under conditions allowing the expression of the IgG1 antibody as defined hereinabove and recovering the produced IgG1 antibody from the culture. A further aspect of the invention relates to a use of a IgG1 antibody as defined hereinabove or as produced by the process as defined hereinabove, a nucleic acid molecule as defined hereinabove, a vector as defined hereinabove or a host as defined hereinabove for the preparation of a pharmaceutical composition for the prevention, treatment or amelioration of an epithelial tumor in a human. Another aspect of the invention relates to a method for the prevention, treatment or amelioration of an epithelial tumor in a human, said method comprising the step of administration of an effective amount of a pharmaceutical composition of the invention or as produced according by the process set forth above. The person skilled in the art, in particular the attending physician can evaluate the successful treatment of the patient in need of administration of the bispecific molecule/bispecific single chain antibody of the invention. Accordingly, the administration scheme as well as the dosage and the administration time may be assessed by said person skilled in the art: A corresponding “amelioration” and/or “treatment” to be assessed is defined below.

The most preferred mode of administration is an intravenous administration over a given time/time period. While the IgG1 antibody as defined herein may be administered per alone, preferred is administration in a pharmaceutically acceptable carrier. Examples of suitable pharmaceutical carriers are well known in the art and include phosphate buffered saline solutions, water, liposomes, various types of wetting agents, sterile solutions, etc. Compositions comprising such carriers can be formulated by well known conventional methods. These pharmaceutical compositions can be administered to the subject at a suitable dose. The dosage regimen will be determined by the attending physician and clinical factors. As is well known in the medical arts, dosages for any one patient depends upon many factors, including the patient's size, body surface area, age, the particular compound to be administered, sex, time and route of administration, general health, and other drugs being administered concurrently. Preparations for parenteral administration include sterile aqueous or non-aqueous solutions, and suspensions. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, and injectable organic esters such as ethyl oleate. Aqueous carriers include water, aqueous solutions, or suspensions, including saline and buffered media. Parenteral vehicles include sodium chloride solution, Ringer's dextrose, dextrose and sodium chloride, lactated Ringer's, or fixed oils. Intravenous vehicles include fluid and nutrient replenishes, electrolyte replenishers (such as those based on Ringer's dextrose), and the like. Preservatives and other additives may also be present such as, for example, antimicrobials, anti-oxidants, chelating agents, and inert gases and the like. In addition, the composition might comprise proteinaceous carriers, like, e.g., serum albumine or immunoglobuline, preferably of human origin. It is envisaged that the co-therapy might comprise, in addition to the proteinaceous IgG1 antibody further biologically active agents, depending on the intended use of the pharmaceutical composition. Such agents might be agents acting on the gastrointestinal system, agents acting as cytostatica, agents preventing hyperurikemia, agents inhibiting immune reactions (e.g. corticosteroids, FK506), drugs acting on the circulatory system and/or agents such as T-cell co-stimulatory molecules or cytokines known in the art. Preferably, the IgG1 antibody as defined herein is formulated in a buffer, a stabilizer and a surfactant. The buffer may be a phosphate, citrate, succinate or acetate buffer. The stabilizer may be (an) amino acid(s) and/or a sugar. The surfactants may be detergents, PEGs, or the like. More preferably, the IgG1 antibody as defined herein is formulated in citrate, lysine, trehalose and Tween 80. As a diluent for said pharmaceutical composition, isotonic saline and Tween 80 is preferred.

The term “amelioration” as used herein refers to an improvement or a moderation in the severity of a disease, i.e. an epithelial tumor. For example, such an amelioration may be the achievement of a stable disease—or even more preferred—a shrinkage of the epithelial tumor(s), i.e. a minimal, partial response or complete response, due to the administration of the pharmaceutical compositions of the invention. “Stable disease” refers to a disease state in which no or no significant tumor progression/growth can be observed or detected by clinical and/or histological diagnostic methods. For example, a shrinkage of the tumor greater than 50% shrinkage of the sum of cross-sectional areas of index lesions may be considered as a “partial response”. A “complete response” denotes a state in which no lesion(s) can be detected any more after treatment. A response with a tumor shrinkage between stable disease and partial response may be considered as a minimal response. For instance, a 20%, 25% or 30% shrinkage of the sum of cross-sectional areas of index lesions may be referred to as a minimal response.

The term “amelioration” as used herein encompasses also a reduction of the number of epithelial tumors. It furthermore denotes the prevention/slowdown of tumor progression. Moreover, an improvement of the overall survival of treated tumor patients in Comparison to non-treated tumor patients may be considered as an “amelioration” as used herein. This applies mutatis mutandis to an improvement of the progression-free survival or the relapse-free survival of treated tumor patients as compared to non-treated tumor patients. In addition, the term “amelioration” can also refer to a reduction of the intensity of the symptoms of an epithelial tumor, resulting e.g. in an improvement of the quality of life of the treated tumor patients.

The term “prevention of an epithelial tumor” as used herein is to be understood as follows: After surgical removal of the primary epithelial tumor(s) from a human patient and/or after chemotherapeutic or radiological treatment of the primary epithelial tumor(s), it may be the case that not all tumor cells could be eliminated from the body. However, these remaining tumor cells may give rise to recurrent cancer, i.e. local recurrence and/or metastases in the patient. Metastasis is a frequent complication of cancer, yet the process through which cancer cells disseminate from the primary tumor(s) to form distant colonies is poorly understood. Metastatic cancers are almost without exception uncurable raising the necessity for new therapeutic modalities. The pharmaceutical composition of the invention can be used to kill these disseminated tumor cells in order to prevent the formation of secondary tumors (originating from the tumor cells remaining in the body after primary therapy). In this way, the pharmaceutical composition helps to prevent the formation of local recurrence and/or metastases in tumor patients.

The success of the anti-tumor therapy may be monitored by established standard methods for the respective disease entities, e.g. by computer-aided tomography, X-ray, nuclear magnetic resonance tomography (e.g. for National Cancer Institute-criteria based response assessment (Cheson (1999), J. Clin. Oncol.; 17(4):1244]), positron-emission tomography scanning, endoscopy, Fluorescence Activated Cell Sorting, aspiration of bone marrow, pleural or peritoneal fluid, tissue/histologies, and various epithelial tumor specific clinical chemistry parameters (e.g. soluble CEA concentration in serum) and other established standard methods may be used. In addition, assays determining T cell activation may be used; see e.g. WO99/054440. Statistics for the determination of overall survival, progression-free survival or relapse-free survival of treated tumor patients in comparison to non-treated tumor patients may also be used.

Preferably, said epithelial tumor is a gastrointestinal adenocarcinoma, a breast adenocarcinoma or a lung adenocarcinoma. Said gastrointestinal adenocarcinoma is more preferably a colorectal, pancreatic, an oesophageal or a gastric adenocarcinoma.

Even more preferred, said pharmaceutical composition of the invention is for the treatment of progressive tumors, late stage tumors, tumor patients with high tumor load/burden, metastatic tumors, or tumor patients with a CEA serum concentration higher than 100 ng/ml. Said CEA serum concentration may be determined e.g. by ELISA.

In another preferred embodiment of the uses or methods of the invention, said pharmaceutical composition as defined hereinabove is suitable to be administered in combination with an additional drug, i.e. as part of a co-therapy. In said co-therapy, an active agent may be optionally included in the same pharmaceutical composition as the IgG1 antibody, or may be included in a separate pharmaceutical composition. In this latter case, said separate pharmaceutical composition is suitable for administration prior to, simultaneously as or following administration of said pharmaceutical composition comprising the IgG1 antibody. The additional drug or pharmaceutical composition may be a non-proteinaceous compound or a proteinaceous compound.

Preferably, said proteinaceous compound or non-proteinaceous compound may be administered simultaneously or non-simultaneously with a IgG1 antibody as defined hereinabove, a nucleic acid molecule as defined hereinabove, a vector as defined as defined hereinabove, or a host as defined as defined hereinabove. Preferably, said subject to be treated is a human.

In a further aspect, the invention relates to a kit comprising a IgG1 antibody as defined hereinabove, a nucleic acid molecule as defined hereinabove, a vector as defined hereinabove, or a host as defined hereinabove.

These and other embodiments are disclosed and encompassed by the description and Examples of the present invention. Recombinant techniques and methods in immunology are described e.g. in Sambrook et al. Molecular Cloning: A Laboratory Manual; Cold Spring Harbor Laboratory Press, 3^(rd) edition 2001; Lefkovits; Immunology Methods Manual; The Comprehensive Sourcebook of Techniques; Academic Press, 1997; Golemis; Protein-Protein Interactions: A Molecular Cloning Manual; Cold Spring Laboratory Press, 2002. Further literature concerning any one of the antibodies, methods, uses and compounds to be employed in accordance with the present invention may be retrieved from public libraries and databases, using for example electronic devices. For example, the public database “Medline”, available on the Internet, may be utilized, for example under http://www.ncbi.nlm. nih.qov/PubMed/medline.html. Further databases and addresses, such as http://www.ncbi.nim.nih.qov/, http://www.infobioaen.fr/, http://www.fmi.ch/bioloqv/research tools.html, http://www.tiqr.or Q/. are known to the person skilled in the art and can also be obtained using, e.g., http://www.lvcos. corm. For tumor-related topics see e.g. http://www.nih.gov or http://www.dkfz.de.

The Figures show:

FIG. 1: Schematic representation of an IgG molecule comprising VH, C_(H)1, hinge, C_(H)2, C_(H)3, VL and CL regions. The CDRs of the VH and VL regions are indicated as black boxes.

FIG. 2: Flow cytometric analysis of periplasmic preparations containing Flag-tagged scFv protein fragments specific for CEA from selected clones. Each of the scFv consists of the murine A5B7 VH region and a human VL region, as described in Example 3. Periplasmic preparations of soluble scFv protein fragments were added to 100,000 to 200,000 CEA-transfected CHO cells. For detection a monoclonal anti-Flag antibody was used followed by a PE-labeled polyclonal anti-mouse antibody. ScFvs binding to cells was measured by an increase in fluorescence intensity as compared to cells that were incubated with PBS alone. Fluorescence intensity is blotted on the X-axis, the number of events is blotted on the Y-axis. The negative control (PBS and detection reagents) is shown as filled curve, the respective scFvs are shown as grey lines. Shifting to the right indicates positive binding to the cells. All of the scFvs, i.e. A-121, A-183, A-240, A-313, A-290, A-315, A4-35, A4-52 and MP2-A5, bind to membrane-bound CEA on CHO cells.

FIG. 3: Flow cytometric analysis of periplasmic preparations containing Flag-tagged scFv protein fragments specific for CEA from selected clones. Each of these scFvs consists of a humanized VH region and the human VL region A240, as described in Example 4. Periplasmic preparations of soluble scFv protein fragments were added to 100,000 to 200,000 CEA-transfected CHO cells. Detection was performed by a monoclonal anti-Flag antibody followed by a PE-labeled polyclonal anti-mouse antibody. ScFvs binding to cells was measured by an increase in fluorescence intensity as compared to cells that were incubated with PBS alone. Fluorescence intensity is blotted on the X-axis, the number of events is blotted on the Y-axis. The negative control (PBS and detection reagents) is shown as filled curve, the respective scFvs are shown as grey lines. Shifting to the right indicates positive binding to the cells. The humanized scFv constructs MP510_(—)3-A5.3, MP510_(—)3-B9.1, and MP510_(—)3-D8.1 bind to membrane-bound CEA on CHO cells. 240 Vlambda.3 is a scFv consisting of the murine A5B7 VH region and the human VL A-240 region. This construct shows also CEA-binding activity.

FIG. 4: ELISA analysis of purified human IgG1 versions of the humanized antibodies A5, B9, D8 and the human IgG1 versions of antibodies CEA I and CEA II as well as antibody-containing culture supernatants. An irrelevant human IgG1 antibody was included as a negative control. Antibody binding was tested on immobilized CEA antigen—and for demonstration of CEA specificity also in the absence of coated CEA antigen. Culture supernatant, 10 ug/ml and 1 ug/ml antibody solutions were added to the +/−antigen coated wells blocked with BSA. Detection was performed by peroxidase labeled polyclonal human IgG antibody (Jackson ImmunoResearch). The signals were measured after appropriate incubation with ABTS solution. Signal strength is plotted on the Y axis. Specific binding of the antibodies CEA I and CEA II as well as the humanized antibodies IgG1 A5, IgG1 B9 and IgG1 D8 to immobilized human CEA antigen could be demonstrated in this experiment.

FIG. 5: Flow cytometric analysis of purified CEA antibodies and the respective negative control (see FIG. 4) using concentrations of 10 ug/ml of antibody. Antibody samples were added to 100,000 to 200,000 CEA positive Kato III cells (A), CEA-transfected CHO cells (B) and CEA-negative CHO cells (C). Detection was performed by a biotinylated polyclonal anti-human IgG antibody (DAKO) followed by PE-labeled Streptavidine (Jackson ImmunoResearch). Antibody binding to cells was measured by an increase in fluorescence intensity as compared to cells that were incubated with the respective isotype control. Fluorescence intensity is blotted on the X-axis, the number of events is blotted on the Y-axis. The negative control (PBS and detection reagents) is shown as filled curve, the respective antibodies are shown as grey lines. Shifting to the right indicates positive binding to the cells. Specific binding of the antibodies CEA I and CEA II as well as the humanized antibodies IgG1 A5, IgG1 B9 and IgG1 D8 to human CEA antigen on cells could be demonstrated in this experiment.

FIG. 6: Cytotoxicity analysis (ADCC assay) of purified human IgG1 versions of the humanized antibodies A5, B9, D8 and the human IgG1 version of antibody CEA II. Target cells (CEA transfected CHO cells) were labeled with chromium 51 and incubated with decreasing amounts of the respective antibodies in the presence of human PBMCs for 18 h and in the presence of two concentrations of soluble human CEA antigen (10 and 1 ug/ml, respectively). Two representative results are shown: CEA II antibody in FIG. 6A and IgG1 A5 antibody in FIG. 6B. These two examples clearly illustrate the absence of an inhibitory cytotoxic effect of soluble CEA for the humanized antibody IgG1 A5 (FIG. 6B), whereas the cytolytic activity of CEA II antibody is dramatically reduced in the presence of 1 ug/ml of soluble CEA and is further reduced below detection in the presence of 10 ug/ml soluble CEA (FIG. 6A).

FIG. 7: Cytolytic inhibition in the presence of soluble CEA antigen was converted into an “inhibitory factor”. This factor is defined as the EC50 in the presence of 10 and 1 ug/ml soluble CEA in the ADCC assay divided by the EC50 in the absence of soluble CEA. It can clearly be shown that CEA II has a dramatically decreased cytolytic activity in the presence of soluble CEA antigen, whereas IgG1 A5-, IgG1 B9- and IgG1 D8-mediated cytolytic activity towards tumor cells is resistant to soluble CEA.

The following Examples illustrate the invention:

EXAMPLE 1 Generation of Cho Cells Transfected with Human CEA (Carcinoembryonic Antigen-Related Cell Adhesion Molecule 5; CEACAM5)

Kato III cells (human gastric carcinoma cell line; ATCC HTB-103), which are CEA positive were used to obtain the total RNA that was isolated according to the instructions of the kit manual (Qiagen, RNeasy Mini Kit). The obtained RNA was used for cDNA synthesis by random-primed reverse transcription. For cloning of the full length sequence of the CEA antigen, the following oligonucleotides were used: 5′ CEACAM5 EcoRI GAATTCGCCACCATGGAGTCTCCCTCGGCCCC (SEQ ID NO. 35) and 3′ CEACAM5 Sal I GTCGACCTATATCAGAGCAACCCC (SEQ ID NO. 36). A PCR (denaturation at 93° C. for 5 min, annealing at 58° C. for 1 min, elongation at 72° C. for 1 min for the first cycle; denaturation at 93° C. for 1 min, annealing at 58° C. for 1 min, elongation at 72° C. for 1 min for 30 cycles; terminal extension at 72° C. for 5 min) was used to amplify the coding sequence. The PCR product was subsequently digested with EcoRI and SalI, ligated into the appropriately digested expression vector pEF-DHFR, and transformed into E. coli. The isolated plasmid DNA was sequenced and compared with the established nucleotide sequence of CEACAM5 (NM_(—)004363 at the National Center for biotechnology information, http://www.ncbi.nlm.nih.gov/; SEQ ID NO. 37) The aforementioned procedures were carried out according to standard protocols (Sambrook, Molecular Cloning; A Laboratory Manual, Cold Spring Harbour Laboratory Press, Cold Spring Harbour, New York (1989; 2001). The clone with the verified nucleotide sequence was transfected into DHFR deficient CHO cells for eukaryotic expression of the construct. Eukaryotic protein expression in DHFR deficient CHO cells was performed as described in Kaufmann (Kaufmann R. J., Methods Enzymol. 185 (1990), 537-566). Gene amplification of the construct was induced by increasing concentrations of MTX to a final concentration of up to 20 nM MTX. The transfected cells were then tested for expression of CEA antigen using an FACS assay. For that purpose, a number of 2.5×10⁵ transfected cells were incubated with the murine monoclonal antibody COL-1 (Neomakers; Fremont, Calif., USA) in a concentration of 5 μg/ml. The binding of the antibody was detected with a R-Phycoerythrin-conjugated affinity purified F(ab′)2 fragment, goat anti-mouse IgG, Fc-gamma fragment specific antibody, diluted 1:100 in 50 μl PBS with 2% FCS (obtained from Dianova, Hamburg, Germany). Cells were analyzed by flow cytometry on a FACS-Calibur (Becton Dickinson, Heidelberg). FACS staining and measuring of the fluorescence intensity were performed as described in Current Protocols in Immunology (Coligan, Kruisbeek, Margulies, Shevach and Strober, Wiley-Interscience, 2002). As a result, the transfectants demonstrated a clearly positive staining for the human CEA antigen.

EXAMPLE 2 Generation and Characterization of IgG1 Antibodies Derived from Murine Monoclonal Antibodies (mAb) A5B7 and T84.66

In order to express full IgG antibody molecules, two vectors have been generated. One of these vectors encoded the heavy chain, whereas the other encoded the light chain. The full IgG molecules have been derived from murine monoclonal antibodies A5B7 (Chester, Int. J. Cancer 57 (1994), 67-72; Harwood, loc. cit.) and T84.66 (Neumaier, Cancer Res. 50 (1990), 2128-34). The respective sequences were extracted from the literature and the corresponding V-regions were gene-synthesized at Entelechon, Germany. These synthesized DNA fragments were used as templates in the following PCR steps.

1. Cloning of Murine Light Chains Based on Antibody CEA I (A5B7) and CEA II (T84.66)

To generate suitable terminal restriction sites, the DNA fragment encoding the VL region of antibody CEA I (A5B7) was reamplified by PCR, resulting in Vkappa fragments with a Bsu36I-site at the 5′-end and a Xho I-site at the 3′-end. The primers 5′-VL CEA I Bsu36I (5′-TTCTCTCCTTAGGTGTCCACTCCGACATTGAGCTCACC CAGTCTCC-3′) (SEQ ID NO. 81) and 3′-VL CEA I Xho I (5′-CATGCACTCGAG CTTGGTCCCTCCACCGAACGTC-3′) (SEQ ID NO. 82) were used for this purpose. This fragment was then subcloned into a pBS-derived plasmid containing a human leader sequence and a murine Ckappa (Hieter et al. 1980 Cell 22: 197-207) region by Bsu36I and XhoI, thereby adding a mammalian leader sequence and a murine Ckappa constant region. Utilizing EcoRI and SalI, CEA I VL-Ckappa DNA was excised from said vector and subcloned into the eukaryotic expression vector pEF-ADA derived from the expression vector pEF-DHFR (Mack et al. (1995) Proc. Natl. Acad. Sci. USA. 92, 7021-5) by replacing the cDNA encoding murine dihydrofolate reductase (DHFR) with that encoding murine adenosine deaminase (ADA). The same procedure was performed with the VLs of antibody CEA-II (T84.66), accordingly, but using different specific primers:

For CEA II (T84.66):

5′-VL CEA II Bsu36I (SEQ ID NO. 83) (5′- TTCTCTCCTTAGGTGTCCACTCCGACATTGTGCTGACCCAATCT CC-3′) and 3′-VL CEA II Xho I (SEQ ID NO. 84) (5′-CATGCACTCGAGCTTGGTCCCCCCACCGAACGTG-3′)

As a result of this experiment, murine light chains based on antibodies CEA I (A5B7), and CEA II (T84.66) have been generated. The amino acid sequence of the VH region of mAb A5B7 is shown in SEQ ID NO. 8, whereas the VL region of CEA I (mAb A5B7) is shown in SEQ ID NO. 10. The amino acid sequence of the VH region of CEA II (mAb T84.66) is shown in SEQ ID NO. 12, whereas the VL region of mAb T84.66 is shown in SEQ ID NO. 14.

2. Cloning of Murine Heavy Chain Variable Domains

From the murine VH regions of CEA I (A5B7) and CEA II (T84.66, the variable region of the heavy chain was reamplified by PCR, generating Bsu36I restriction sites at both ends. For CEA I (A5B7) the combination of the following two primers was used: 5′-primer 5′-CEA I VH-Bsu36I (5′-TTCTCTCCTTAGGTGTCCACTCCCAGGTCCAACTGCAGGAGTCAGG-3′) (SEQ ID NO. 87) and 3′-primer 3′-CVH-Bsu36I (5′-GACTCACCTGAGGAGACGGTGACCGT GGTCCCTTGG-3′) (SEQ ID NO. 88), for CEA II (T84.66) the combination of the following two primers was used: 5′-primer 5′-CEA II VH-Bsu36I (5′-TTCTCTCCTTAGGTGTCCACTCCGAGGTTCAGCTGCAGCAGTCTGG-3′) (SEQ ID NO. 89) and 3′-primer 3′-CEA II VH-Bsu36I (5′-GACTCACCTGAGGAGACGGTGAC TGAGGTTCCTTGACC-3′) (SEQ ID NO. 90).

The resulting DNA-fragments were then subcloned using these restriction sites into the eukaryotic expression vector pEF-DHFR already containing a eukaryotic leader sequence and a DNA-fragment encoding the human IgG1 heavy chain constant region (see Raum, Cancer Immunol Immunother. 50 (2001):141-50). The heavy chain variable regions were thus inserted between the leader and the heavy chain constant region.

As a result of this experiment, vectors encoding murine heavy chain variable domains linked to said human IgG1 constant region have been generated. The amino acid sequence of the VH region of mAb A5B7 is shown in SEQ ID NO. 8, whereas the VL region of CEA I (mAb A5B7) is shown in SEQ ID NO. 10. The amino acid sequence of the VH region of CEA II (mAb T84.66) is shown in SEQ ID NO. 12, whereas the VL region of mAb T84.66 is shown in SEQ ID NO. 14.

3. Expression of the Full IgG Proteins

In order to express full IgG1 antibodies, a plasmid encoding for one (murine) light chain and a plasmid encoding for one heavy chain (murine VH/human IgG1 constant region) generated as set forth above were co-transfected into HEK cells according to standard protocols for transient protein expression and the cells were cultured to allow the expression and production of the immunoglobulins into the culture medium. In this manner, huIgG1 CEA I derived from antibody CEA I (A5B7) and huIgG1 CEA II derived from antibody CEA II (T84.66) were produced. Said huIgG1 antibody constructs consist of a murine variable (V) region derived from CEA I (A5B7) or CEA II (T84.66), a murine constant (C) light chain (Ckappa) region and human constant heavy chain CH1, CH2, CH3 and hinge regions (the human IgG1 heavy chain constant region is described in Raum, Cancer Immunol Immunother. 50 (2001): 141-50). After the respective production period, the supernatants were harvested and the human immunoglobulins were isolated via Protein A chromatography according to standard protocols for the purification of immunoglobulins. Culture supernatants, as well as purified immunoglobulins were then used for further characterization experiments.

4. Characterization of the IgG1 Antibodies Generated Above

4.1 Binding to Immobilized Soluble CEA (sCEA) Antigen

Culture supernatants of heavy+light chain double transfectants as well as the corresponding preparations of purified antibody were tested for binding on immobilized soluble CEA (sCEA; Abcam, Ltd, Cambridge UK) antigen by ELISA according to standard procedures. The antibodies huIgG1 CEA I derived from antibody CEA I (A5B7) and huIgG1 CEA II derived from antibody CEA II (T84.66) generated as set forth above showed distinct binding to the immobilized sCEA antigen as compared to the negative control and no binding in an equivalent setting with the difference that no sCEA antigen was coated (as shown in FIG. 4).

4.2 Binding to Membrane Bound CEA

Purified antibody preparations of huIgG1 CEA I derived from antibody CEA I (A5B7) and huIgG1 CEA II derived from antibody CEA II (T84.66) were tested by FACS analysis on the CEA-positive gastric cancer cell line Kato III, CEA-transfected CHO-cells and untransfected CHO-cells.

2×10⁵ cells were incubated with purified antibody preparations (typically 10-20 μg/ml). Detection of cell-bound antibodies was carried out with FITC labeled anti mouse IgG- or anti human IgG antibodies (typically 10-20 μg/ml). Incubation was carried out for 20-40 min. on ice.

huIgG1 CEA I derived from antibody CEA I (A5B7) and huIgG1 CEA II derived from antibody CEA II (T84.66) showed distinct binding to the CEA positive cells. None of the IgG1 antibodies showed binding to untransfected CHO cells. IgG-controls were negative on Kato III cells, CHO/CEA-cells and untransfected CHO cells (as shown in FIGS. 5A, B and C).

4.3 Antibody Dependent Cellular Cytotoxicity (ADCC) Assay (⁵¹Cr Release Assay)

For the ⁵¹Cr release assay, human peripheral blood mononuclear cells (PBMCs) as effector cells were isolated from healthy donors. The PBMCs were separated by Ficoll density gradient centrifugation with a subsequent 100×g centrifugation step. Unstimulated PBMCs (5×10⁵ cells) were added in a volume of 100 μl of RPMI 1640 medium with 10% FCS to each well of a flat bottomed microtiter plate and incubated overnight at 37° C. As target cells, CEA-transfected CHO cells have been used. Target cells were labeled for 2 h with ⁵¹Cr. Labeled target cells (50.000 cells) and antibodies in different concentrations (10 pg/ml-10 μg/ml) were added to the PBMCs and incubated for 18 h at 37° C. This assay has been carried out in the absence of soluble CEA (sCEA) antigen. Corresponding non-binding isotypes were used as negative controls. Specific lysis was calculated as ((cpm, experimental release)−(cpm, spontaneous release))/((cpm, maximal release)−(cpm, spontaneous release)). huIgG1 CEA I derived from antibody CEA I (A5B7) and huIgG1 CEA II derived from antibody CEA II (T84.66) proved to mediate significant cytotoxicity for the CEA positive CHO cells in this ⁵¹Cr release assay as compared to the negative control.

In a second cytotoxicity experiment, the antibody samples were pre-incubated with soluble CEA (sCEA) antigen for 20 min under agitation and then mixed with the labeled target cells and the human PBMCs. Otherwise, the assay has been performed as described above. Soluble CEA (sCEA) antigen has been used in different concentrations, i.e. 1 μg/ml and 10 μg/ml.

In the presence of soluble CEA, especially at the higher concentrations, huIgG1 CEA II derived from antibody CEA II (T84.66) showed reduced cytotoxic (ADCC) activity. In contrast, huIgG1 CEA I derived from antibody CEA I (A5B7) showed no significant decrease of cytotoxic activity as compared to the activity in the absence of soluble CEA. Thus, cytotoxicity against CEA positive tumor cells mediated by huIgG1 CEA I derived from antibody CEA I (A5B7) is resistant to soluble CEA.

In summary, it has been found that the cytotoxic activity (ADCC) directed against tumor cells of huIgG1 CEA I derived from antibody CEA I (A5B7) is resistant to even high concentrations of soluble CEA antigen. This finding is entirely unexpected in view of the fact that this IgG1 antibody binds to soluble CEA antigen. For example, when an IgG1 antibody construct derived from monoclonal antibody T84.66 has been tested, this antibody was highly sensitive to soluble CEA antigen, ie. the cytotoxic activity (ADCC) has been blocked by soluble CEA antigen. This antibody has also been found to be capable of binding to soluble CEA. In view of this, it was concluded that soluble CEA antigen prevents huIgG1 CEA II derived from antibody CEA II (T84.66) from exerting its antibody-mediated cytotoxic activity. In contrast, the IgG1 CEA I antibodies derived from antibody CEA I (A5B7) as defined herein are resistant to the presence of even high levels of soluble CEA in their cytotoxic activity towards tumor cells.

EXAMPLE 3 Selection of Human VL Regions

In order to provide for IgG1 antibodies with reduced immunogenicity when being administered to cancer patients, humanized IgG1 antibodies with resistance to soluble CEA antigen have been generated. In a first step, human VL regions with resistance to soluble CEA have been isolated. Thus, the aim of this experiment is the selection of human VL regions which can pair with the maternal, murine VH of monoclonal antibody (mAb) A5B7.

1. Biotinylation of Soluble Human CEA Antigen

For phage library selection, soluble CEA antigen was biotinylated. Biotinylation was accomplished in PBS containing 5% DMSO (Sigma) with a fifteenfold molar excess of EZ-Link Sulfo NHS-LC-LC-Biotin (Pierce) for 1 hour at room temperature in a sample mixer (Dynal). For the separation of free Biotin and biotinylated CEA antigen, the assay was excessively dialized against PBS according to standard protocols. The retained bioactivity of the biotin-labeled CEA was confirmed in ELISA binding experiments.

2. Isolation of RNA from Human B-Cells

100 mL blood were taken from five healthy human donors. Peripheral blood mononuclear cells (PBMCs) were isolated by a ficoll-gradient according to standard methods. Total RNA was isolated from the isolated cells using the RNeasy® Midi Kit (QIAGEN) following the manufacturer's instructions. cDNA was synthesized according to standard methods (Sambrook, Cold Spring Harbor Laboratory Press 1989, 2001).

3. PCR-Amplification of Variable Light Chain Regions (VL-Regions)

For the isolation of light chain V-region DNA, RT-PCR was carried out using V-kappa-(5′-huVK1-SacI-2001 (5′-GAGCCGCACG AGCCCGAGCT CCAGATGACC CAGTCTCC-3′) (SEQ ID NO. 38), 5′-huVK2/4-SacI-2001 (5′-GAGCCGCACG AGCCCGAGCT CGTGATGACY CAGTCTCC-3′) (SEQ ID NO. 39), 5′-huVK3-SacI-2001 (5′-GAGCCGCACG AGCCCGAGCT CGTGWTGACR CAGTCTCC-3′) (SEQ ID NO. 40), 5′-huVK5-SacI-2001 (5′-GAGCCGCACG AGCCCGAGCT CACACTCACG CAGTCTCC-3′) (SEQ ID NO. 41), 5′-huVK6-SacI-2001 (5′-GAGCCGCACG AGCCCGAGCT CGTGCTGACT CAGTCTCC-3′) (SEQ ID NO. 42), 3′-hu-Vk-J1-SpeI-BsiWI (5′-GACGACACTA GTTGCAGCCA CCGTACGTTT GATTTCCACC TTGGTCC-3′) (SEQ ID NO. 43), 3′-hu-Vk-J2/4-SpeI-BsiWI (5′-GACGACACTA GTTGCAGCCA CCGTACGTTT GATCTCCASC TTGGTCC-3′) (SEQ ID NO. 44), 3′-hu-Vk-J3-SpeI-BsiWI (5′-GACGACACTA GTTGCAGCCA CCGTACGTTT GATATCCACT TTGGTCC-3′) (SEQ ID NO. 45), 3′-hu-Vk-J5-SpeI-BsiWI (5′-GACGACACTA GTTGCAGCCA CCGTACGTTT AATCTCCAGT CGTGTCC-3′) (SEQ ID NO. 46)) and V lambda (5′-huVL1a-SacI-2001 (GAG CCG CAC GAG CCC GAG CTC GTG TTG ACG CAG CCG CCC TC) (SEQ ID NO. 47), 5′-huVL1b-SacI-2001 (GAG CCG CAC GAG CCC GAG CTC GTG CTG ACT CAG CCA CCC TC) (SEQ ID NO. 48), 5′-huVL2-SacI-2001 (GAG CCG CAG GAG CCC GAG CTC GCC CTG ACT CAG CCT SCC TCC GT) (SEQ ID NO. 49), 5′-huVL4-SacI-2001 (ACC TGC GAG CTC GTG CTG ACT CAR YCM YCC TCT GC) (SEQ ID NO. 50), 5′-huVL5-SacI-2001 (ACC TGC GAG CTC GTG CTG ACT CAG CCR SCT TCC) (SEQ ID NO. 51), 5′-huVL6-SacI-2001 (ACC TGC GAG CTC ATG CTG ACT CAG CCC CAC TC) (SEQ ID NO. 52), 5′-huVL3/9-SacI-2001 (GAG CCG CAC GAG CCC GAG CTC GWG CTG ACT CAG CCA CCY TC) (SEQ ID NO. 53), 5′-huVL7/8-SacI-2001 (GAG CCG CAC GAG CCC GAG CTC GTG GTG ACY CAG GAG CCM TC) (SEQ ID NO. 54), 3′-hu-Vlam-BlnI-SpeI-2001 (CGT GGG ACT AGT CTT GGG CTG ACC TAG GAC GGT) (SEQ ID NO. 55), 3′-hu-Vlam2-BlnI-SpeI-2002: CGT GGG ACT AGT CTT GGG CTG ACC GAG GAC GGT) (SEQ ID NO. 56) primer sets.

RNA from human B-cells was transcribed into cDNA (as described above) and used as template DNA in PCR reactions. Per PCR reaction, one 5′-primer was combined with one 3′-primer. The number of different PCR reactions was determined by the number of possible combinations of 5′- and 3′-primers. The following PCR-program was used for amplification: Denaturation at 94° C. for 15 seconds, primer annealing at 52° C. for 50 seconds and primer extension at 72° C. for 90 seconds were performed over 40 cycles, followed by final extension at 72° C. for 10 minutes. Light chain DNA V-fragments were then isolated according to standard protocols.

4. Library Construction—Cloning of the Human VL Pool

A phage display library was generally constructed based on standard procedures, as for example disclosed in “Phage Display: A Laboratory Manual”; Ed. Barbas, Burton, Scott & Silverman; Cold Spring Harbor Laboratory Press, 2001.

The primers chosen for PCR amplification gave rise to 5′-SacI and 3′-SpeI recognition sites for the light chain V-fragments. Four ligation reactions were set up, each consisting of 400 ng of light chain fragments (SacI-SpeI digested, 2×kappa and 2×lambda) and 1400 ng of the phagemid pComb3H5BHis (SacI-SpeI digested; large fragment; this vector is described in the thesis dissertation of Dr. Ralf Lutterbüse. The four resulting antibody V-light chain pools were then each transformed into 300 μL of electrocompetent Escherichia coli XL1 Blue by electroporation (2.5 kV, 0.2 cm gap cuvette, 25 mF, 200 Ohm, Biorad gene-pulser) resulting in library sizes of

kappa1: 2×10⁸ kappa2: 6×10⁷ lambda1: 9×10⁷ lambda2: 6×10⁷ independent clones.

Kappa (light chain) DNA-fragments from the different PCR amplifications were weighted for each ligation as follows: Each 5′-primer defines a specific group. Within these groups the 3′-primers define the subgroups. The kappa subgroups were weighted 1:2:1:1 corresponding to the primers 3′-hu-Vk-J1-SpeI-BsiWI:3′-hu-Vk-J2/4-SpeI-BsiWI:3′-hu-Vk-J3-SpeI-BsiWI:3′-hu-Vk-J5-SpeI-BsiWI. The groups were weighted according to their germline distribution 1:1:1:0.2:0.2 corresponding to the primers 5′-huVK1-Sac-2001:5′-huVK3-Sac-2001:5′-huVK2/4-Sac-2001:5′-huVK5-Sac-2001:5′-huVK6-Sac-2001.

Lambda (light chain) DNA-fragments from the different PCR amplifications were weighted for each ligation as follows: Each 5′-primer defines a specific group. Within these groups the 3′-primers define the subgroups. The lambda subgroups were weighted 3:1 corresponding to the primers 3′-hu-Vlam-BlnI-SpeI-2001:3′-hu-Vlam2-BlnI-SpeI-2002.

The groups were weighted according to their germline distribution 1:1:2:2:2:3 corresponding to the primers 5′-huVL1a-SacI-2001:5′-huVL1b-SacI-2001:5′-huVL2-SacI-2001:5′-huVL4-SacI-2001+5′-huVL5-SacI-2001:5′-huVL6-SacI-2001+5′-huVL7/8-SacI-2001:5′-huVL3/9-SacI-2001.

After electroporation each transformed E. coli culture was incubated in SOC broth (Fluka) for phenotype expression. The two kappa cultures were combined as well as the two lambda cultures. The resulting kappa culture and the resulting lambda culture were then each incubated in 500 mL of SB selection medium containing 50 μg/mL carbenicillin and 2% w/v glucose overnight. The next day, cells were harvested by centrifugation and plasmid preparation was carried out using a commercially available plasmid preparation kit (Qiagen).

5. Construction of the Antibody Library—Human VL—Maternal VH

PCR was performed to amplify the maternal VH of mAb A5B7 from a vector containing said maternal VH. For amplification a PCR protocol according to standard procedures was followed using the 5′-primer 5′-AVH-XhoI (5′-GTC ACA CTC GAG TCA GGA GGA GGC TTG GTA C-3′) (SEQ ID NO. 57) and the 3′-primer 3′-AVH-BstEII (5′-GTC ACA GGT GAC CGT GGT CCC TTG GCC CCA G-3′ (SEQ ID NO. 58). After purification of the approximately 350 bp amplification product from an analytical agarose gel, the DNA fragment was cut with the restriction enzymes BstEII and XhoI. The phagemid pComb3H5BHis (this vector is described in the thesis dissertation of Dr. Ralf Lutterbüse) was digested accordingly and the large fragment was ligated with the above mentioned fragment. After transformation into E. coli XL1 blue, a single clone was cultivated in 100 mL SB medium (containing 50 μg/mL carbenicilline) and the plasmid was prepared according to standard protocols. The successful cloning was confirmed by sequencing the insert (Sequiserve, Munich). This vector pComb3H5BHis/maternalVH of mAb A5B7 was restricted with the restriction enzymes SacI and SpeI. The large vector fragment was isolated. Plasmid-DNA containing the Vkappa- and the Vlambda library was restricted with the restriction enzymes SacI and SpeI. The small Vkappa—and the respective Vlambda fragment (each approximately 350 bp) were isolated according to standard protocols. 1200 ng of the vector fragment were ligated with a mix of each 200 ng of both the Vkappa and the Vlambda fragments. The ligation reaction was transformed into 300 μL of electrocompetent E. coli XL1 Blue by electroporation (2.5 kV, 0.2 cm gap cuvette, 25 mF, 200 Ohm) resulting in a total scFv library size of 1.2×10⁸ independent clones.

After phenotype expression and slow adaptation to carbenicillin, the antibody library was transferred into SB-Carbenicillin (50 μg/mL) selection medium. The antibody library was then infected with an infectious dose of 1×10¹² particles of helper phage VCSM13 resulting in the production and secretion of filamentous M13 phage, wherein each phage particle contained single stranded pComb3H5BHis-DNA encoding a half-human scFv-fragment and displayed the corresponding scFv-protein as a translational fusion to phage coat protein III.

6. Phage Display Selection of a Human VL

The phage particles carrying the scFv-repertoire were harvested from the culture supernatant by PEG8000/NaCl precipitation and centrifugation. Then approximately 1×10¹¹ to 1×10¹² scFv phage particles were resuspended in 0.5 mL of TBS/1% BSA and incubated with biotinylated soluble CEA, that was immobilized in Streptavidin coated wells of an ELISA plate (Nunc) for 1 h. A 10 μg antigen/ml PBS solution (50 μl) was incubated for over night at 4° C. in the Streptavidin coated wells, washed once with water, followed by blocking for 1 hour at 37° C. with 200 μl of 3% BSA in TBS, that was removed after incubation.

scFv phage that did not specifically bind to the target antigen were eliminated by washing steps with TBS/0.05% Tween. This washing procedure was repeated up to 10 times in further rounds.

After washing, binding entities were eluted by using HCl-glycine, pH 2.2. Following neutralization with 2 M Tris, pH 12, the eluate was used for infection of a fresh uninfected E. coli XL1 Blue culture.

To elute remaining high binding entities 50 μL of a fresh E. coli XL1 blue culture (OD600≧0.5) were added to the wells and incubated for 15 minutes. Both cultures were then mixed and cells successfully transduced with a phagemid copy, encoding a human scFv-fragment, were again selected for carbenicillin resistance and subsequently infected with VCMS13 helper phage to start the second round of antibody display and in vitro selection.

Plasmid DNA corresponding to 4 rounds of panning was isolated from E. coli cultures. For the production of soluble scFv-protein, VH-VL-DNA fragments were excised from the plasmids (XhoI-SpeI), and cloned via the same restriction sites in the plasmid pComb3H5BFlag/His, in which the expression construct (e.g. scFv) includes a Flag-tag (TGDYKDDDDK) (SEQ ID NO. 59) between the scFv and the His 6-tag and the additional phage proteins are deleted.

After ligation each pool (different rounds of panning) of plasmid DNA was transformed into 100 μL heat shock competent E. coli TG1 and plated onto carbenicillin LB-agar. Single colonies were picked and inoculated into 120 μL of LB carb (50 μg/mL) 1% glucose in 96-well plates (Greiner). The wells were sealed with a semipermeable membrane (Greiner) and the plates were incubated overnight at 37° C. in a shaking incubator (master plate). Then 10 μL of the master plate cultures were transferred into a second 96 well plate (working plate) containing 90 μL LB carb (50 μg/mL) 0.1% glucose per well. After incubation for 4 h in a 37° C. shaking incubator, scFv production was induced by adding 20 μL LB carb 6 mM IPTG to each well. After another incubation step overnight at 30° C. with shaking, cells were lysed in a 1 h incubation at room temperature with 40 μL lysis buffer (400 mM boric acid, 320 mM NaCl, 4 mM EDTA pH 8, 2.5 mg/mL lysozyme). Residual cells and cell debris were separated by centrifugation for 12 minutes at 1,900×g (Hettich).

The supernatants containing scFv molecules were then tested for binding in flow cytometric binding assays. CHO cells transfected with human CEA were used as CEA-positive cell line. Cell binding assays were carried out by initially incubating between 100,000 and 200,000 cells with periplasmic preparation containing human scFv or relevant controls. After incubation the cells were washed in PBS/1% FCS (fetal calf serum) and further incubated with 5-10 μg/ml of anti-FLAG M2 antibody (Sigma). After the cells had again been washed, they were incubated with polyclonal, PE-labeled anti-mouse antibodies (Dianova) and subsequently analyzed by flow cytometry. Approximately 600 clones were tested for binding signals on CEA-positive CHO cells. 27 positive clones were obtained. After sequencing of the respective scFv DNA, a total of 9 different sequences were obtained.

FIG. 2 depicts binding of the nine different half-human scFv (i.e. murine A5B7 VH-human VL) constructs to the CEA-transformed CHO cell line as measured by flow cytometric analysis. Said Figure contains multiple diagrams, one for each construct tested. In any given diagram, the black distribution shows fluorescence intensity for cells incubated only with PBS alone in the absence of any construct but with all appropriate detection agents as used for detection of scFvs. In this way, any fluorescence shift observed can be definitely attributed to scFv construct rather than detection agents or buffer. Shifts in fluorescence which are indicative of construct binding to the respective cell line are depicted by a gray line in each diagram. Generally, a shift of higher magnitude away from, i.e. further to the (black) control indicates stronger binding, whereas a shift of lower magnitude away from, i.e. closer to the (black) control indicates weaker binding.

It can be seen from FIG. 2 that the constructs A-121, A-183, A-240, A-313, A-290, A-315, A4-35, A4-52, MP2-A5 show clearly discernable shifts in fluorescence intensity as compared to the respective control, indicative of binding of the scFvs to membrane-bound CEA on the CHO target cells. In the following, the human VL region of scFv A-240 has been selected and used for the isolation of a human VH region. Said human A-240 VL region is encompassed e.g. in SEQ ID NO. 2.

EXAMPLE 4 Construction of the Antibody Libraries and Phage Display Selection of Humanized VH Regions Resistant to Soluble CEA Antigen

The aim of the following experiments is the selection of a set of humanized VH regions resistant to soluble CEA antigen that pair with the human VL region of scFv A-240, selected as described in Example 3. Said human A-240 VL region is encompassed e.g. in SEQ ID NO. 2.

1. Isolation of RNA from Peripheric Blood Mononuclear Cells (PBMCs)

100 mL blood were taken from five healthy human donors. Peripheral blood mononuclear cells (PBMCs) were isolated by a ficoll-gradient according to standard methods. Total RNA was isolated from PBMCs using the RNeasy® Midi Kit (QIAGEN) following the manufacturer's instructions. cDNA was synthesized according to standard methods (Sambrook, Cold Spring Harbor Laboratory Press 1989, 2001).

2. PCR-Amplification of Variable Heavy Chain Regions (VH-Regions)

The VH library was constructed and named Lib 134-VH. This VH-library consists of the human repertoire of FR1-CDR1-FR2-CDR2-FR3 from the PCR amplified VH-regions of the above described PBMC pool, linked operatively to the VH CDR3 of the maternal antibody followed by a human FR4 germline sequence.

For the isolation of human template VH-regions, RT-PCR was carried out using a 5′-VH-specific primer set (5′-huVH1,3,5-XhoI-2001 (5′-AGG TGC AGC TGC TCG AGT CTG G-3′) (SEQ ID NO. 60), 5′-huVH4-XhoI-2001 (5′-CAG GTG CAG CTG CTC GAG TCG GG-3′) (SEQ ID NO. 61), 5′-huVH4B-XhoI-2001 (5′-CAG GTG CAG CTA CTC GAG TGG GG-3′) (SEQ ID NO. 62)) and a set of two 3′-VH-specific primers (3′-hu-VH-BstEII-2001 (5′-CTG AGG AGA CGG TGA CC-3′) (SEQ ID NO. 63), 3′-hu-VH-J3-BstEII-2001 (5′-CTG MG AGA CGG TGA CC-3′) (SEQ ID NO. 64)). Per PCR reaction, one 5′-primer was combined with one 3′-primer; the number of different PCR reactions was determined by the number of possible combinations of 5′- and 3′-primers. The PBMC cDNA of five donors was used as a source of VH-genes. The following PCR-program was used for amplification: Denaturation at 94° C. for 15 seconds, primer annealing at 52° C. for 50 seconds and primer extension at 72° C. for 60 seconds was performed over 40 cycles, followed by final extension at 72° C. for 10 minutes. The amplification products with a size of approximately 350 bp were isolated according to standard methods.

For the isolation of Lib 134-VH-regions, RT-PCR was carried out in two steps. First, the human heavy chain VH-segments (FR1-CDR1-FR2-CDR2-FR3) were PCR-amplified from the isolated template VH fragments using the same 5′-VH-specific primer set as described above (5′-huVH1,3,5-XhoI-2001, 5′-huVH4-XhoI-2001, 5′-huVH4B-XhoI-2001; SEQ ID NOs. 60 to 62) and a 3′-specific primer set (3′-A134-VH1A (5′-GTA GTC AAA GTA GM CCG TAG CCC CCT ATC TCT YGC ACA GTA ATA CAC GGC-3′) (SEQ ID NO. 65), 3′-A134-VH1B (5′-GTA GTC AAA GTA GM CCG TAG CCC CCT ATC TCT YGC ACA GTA ATA CAY RGC-3′) (SEQ ID NO. 66), 3′-A134-VH3A (5′-GTA GTC AAA GTA GM CCG TAG CCC CCT ATC TCT NGY ACA GTA ATA CAC RGC-3′) (SEQ ID NO. 67), 3′-A134-VH3B (5′-GTA GTC AAA GTA GM CCG TAG CCC CCT ATC TCT NGC ACA GTA ATA CM RGC-3′) (SEQ ID NO. 68), 3′-A134-VH4 (5′-GTA GTC AAA GTA GM CCG TAG CCC CCT ATC TCT SGC ACA GTA ATA CAC RGC-3′) (SEQ ID NO. 69)) for the human VH subfamilies 1, 3 and 4 matching in the very terminal region of FR3.

The following primer combinations were used:

a) 5′-huVH1,3,5-XhoI-2001×3′-A134-VH1A b) 5′-huVH1,3,5-XhoI-2001×3′-A134-VH1B c) 5′-huVH1,3,5-XhoI-2001×3′-A134-VH3A d) 5′-huVH1,3,5-XhoI-2001×3′-A134-VH3B e) 5′-huVH4-XhoI-2001×3′-A134-VH4 f) 5′-huVH4B-XhoI-2001×3′-A134-VH4

Per PCR reaction, one 5′-primer was combined with the 3′-primer; the number of different PCR reactions was determined by the number of possible combinations of 5′- and the 3′-primer. The following PCR-program was used for amplification: Denaturation at 94° C. for 15 seconds, primer annealing at 52° C. for 50 seconds and primer extension at 72° C. for 90 seconds was performed over 40 cycles, followed by final extension at 72° C. for 10 minutes. Through this PCR step and the respective 3′-primer sequence, the human VH segments are prolonged for a part of the maternal VH CDR3, which then in turn is the priming site for the second step PCR 3′-primer. These VH-(FR1-CDR1-FR2-CDR2-FR3) DNA-fragments were then used as templates in a second PCR reaction using again the respective 5′VH-specific primer and a universal 3′ primer matching to the universal 3′-terminus of the amplified DNA-fragments (3′ A134-JH6-BstEII, 5′-CGA GAC GGT GAC CGT GGT CCC TTG GCC CCA GTA GTC AAA GTA GM CCG TAG CC-3′) (SEQ ID NO. 70).

The following PCR-program was used for amplification:

Denaturation at 94° C. for 15 seconds, primer annealing at 52° C. for 50 seconds and primer extension at 72° C. for 60 seconds were performed over 40 cycles, followed by final extension at 72° C. for 10 minutes. The DNA V-fragments were isolated according to standard protocols.

3. Library Construction—Cloning of the Human VH Pool

In a second round of the foregoing method, the human VL of scFv A-240 identified in the first, previous selection (see Example 3) was chosen, and subsequently combined with the library of human VH fragments with the aim of generating a human scFv. A phage display library was generally constructed based on standard procedures, as for example disclosed in “Phage Display: A Laboratory Manual”; Ed. Barbas, Burton, Scott & Silverman; Cold Spring Harbor Laboratory Press, 2001.

Heavy chain DNA-fragments from the different PCR amplifications were weighted for each ligation as follows:

a:b:c:d:e:f=3:1:3:1:1:1, wherein a-f have the following meanings: a) derived from initial primer combination 5′-huVH1,3,5-XhoI-2001×3′-A134-VH1A b) derived from initial primer combination 5′-huVH1,3,5-XhoI-2001×3′-A134-VH1B c) derived from initial primer combination 5′-huVH1,3,5-XhoI-2001×3′-A134-VH3A d) derived from initial primer combination 5′-huVH1,3,5-XhoI-2001×3′-A134-VH3B e) derived from initial primer combination 5′-huVH4-XhoI-2001×3′-A134-VH4 f) derived from initial primer combination 5′-huVH4B-XhoI-2001×3′-A134-VH4

One ligation reaction was set up consisting of 400 ng of human Lib 134-VH fragment pool (XhoI-BstEII digested) and 1200 ng of the plasmid pComb3H5BHis/A-240 VL (the DNA encoding the VL region of scFv A-240 was cloned via the restriction sites SacI and SpeI into pComb3H5BHis according to standard procedures). The resulting antibody human VH pool was then transformed into 300 μL of electrocompetent Escherichia coli XL1 Blue by electroporation (2.5 kV, 0.2 cm gap cuvette, 25 mF, 200 Ohm, Biorad gene-pulser) resulting in a library size of 0.8×10⁸ independent clones in total.

After electroporation the assay was incubated in SOC broth (Fluka) for phenotype expression. The cultures were then each incubated in 500 mL of SB selection medium containing 50 μg/mL carbenicillin and 2% v/v glucose overnight. The next day, cells of the cultures were harvested by centrifugation and plasmid preparation was carried out using a commercially available plasmid preparation kit (Qiagen) to preserve the DNA library.

1.5 μg of this plasmid pool encoding the respective scFv pool were then electroporated into E. coli XL1blue (2.5 kV, 0.2 cm gap cuvette, 25 mF, 200 Ohm, Biorad gene-pulser) resulting in a library size of 2.4×10⁹ independent clones in total. After phenotype expression and slow adaption to carbenicillin the antibody library was transferred into SB-Carbenicillin (50 μg/mL) selection medium. The antibody library was then infected with an infectious dose of 1×10¹² particles of helper phage VCSM13 resulting in the production and secretion of filamentous M13 phage, wherein each phage particle contained single stranded pComb3H5BHis-DNA encoding a human scFv-fragment and displayed the corresponding scFv-protein as a translational fusion to phage coat protein III.

4. Phage Display Selection of a Human VH

The phage particles carrying the human scFv-repertoire were harvested from the culture supernatant by PEG8000/NaCl precipitation and centrifugation. Then approximately 1×10¹¹ to 1×10¹² scFv phage particles were resuspended in 0.5 mL of TBS/1% BSA and incubated with biotinylated soluble CEA, that was immobilized in Streptavidin coated wells of an ELISA plate (Nunc) for 1 h. A 10 μg antigen/ml PBS solution (50 μl) was incubated for over night at 4° C. in the Streptavidin coated wells, washed once with water, followed by blocking for 1 hour at 37° C. with 200 μl of 3% BSA in TBS, that was removed after incubation.

scFv phage that did not specifically bind to the target antigen were eliminated by washing steps with TBS/0.05% Tween. This washing procedure was repeated up to 10 times in further rounds.

After washing, binding entities were eluted by using HCl-glycine, pH 2.2. Following neutralization with 2 M Tris, pH 12, the eluate was used for infection of a fresh uninfected E. coli XL1 Blue culture.

To elute remaining high binding entities 50 μL of a fresh E. coli XL1 blue culture (OD600≧0.5) were added to the wells and incubated for 15 minutes. Both cultures were then mixed and cells successfully transduced with a phagemid copy, encoding a human scFv-fragment, were again selected for carbenicillin resistance and subsequently infected with VCMS13 helper phage to start the second round of antibody display and in vitro selection.

Plasmid DNA corresponding to 4 rounds of panning was isolated from E. coli cultures. For the production of soluble scFv-protein, VH-VL-DNA fragments were excised from the plasmids (XhoI-SpeI), and cloned via the same restriction sites in the plasmid pComb3H5BFlag/His, in which the expression construct (e.g. scFv) includes a Flag-tag (TGDYKDDDDK; SEQ ID NO. 59) between the scFv and the His 6-tag and the additional phage proteins are deleted.

After ligation each pool (different rounds of panning) of plasmid DNA was transformed into 100 μL heat shock competent E. coli TG1 and plated onto carbenicillin LB-agar. Single colonies were picked and inoculated into 120 μL of LB carb (50 μg/mL) 1% glucose in 96-well plates (Greiner). The wells were sealed with a semipermeable membrane (Greiner) and the plates were incubated overnight at 37° C. in a shaking incubator (master plate). Then 10 μL of the master plate cultures were transferred into a second 96 well plate (working plate) containing 90 μL LB carb (50 μg/mL) 0.1% glucose per well. After incubation for 4 h in a 37° C. shaking incubator, scFv production was induced by adding 20 μL LB carb 6 mM IPTG to each well. After another incubation step overnight at 30° C. with shaking, cells were lysed in a 1 h incubation at room temperature with 40 μL lysis buffer (400 mM boric acid, 320 mM NaCl, 4 mM EDTA pH 8, 2.5 mg/mL lysozyme). Residual cells and cell debris were separated by centrifugation for 12 minutes at 1,900×g (Hettich).

The supernatants containing scFv molecules were then tested for binding in flow cytometric binding assays.

CHO cells transfected with human CEA were used as CEA-positive cell line. Cell binding assays were carried out by initially incubating between 100,000 and 200,000 cells with periplasmic preparation containing human scFv or relevant controls. After incubation the cells were washed in PBS/1% FCS (fetal calf serum) and further incubated with 5-10 μg/ml of anti-FLAG M2 antibody. After the cells had again been washed, they were incubated with polyclonal, PE-labeled anti-mouse antibodies (Dianova) and subsequently analyzed by flow cytometry. 46 clones were tested for binding signals on CEA-positive CHO cells. All of them showed positive signals. After sequencing of the respective scFv DNA a total of 9 different sequences were obtained, eight of which displayed a high degree of homology. The humanized constructs MP510_(—)3-A5.3 (MP510-A5; SEQ ID NO. 2), MP510_(—)3-B9.1 (MP511-B9; SEQ ID NO. 4), MP510_(—)3-D8.1 (MP511-D8; SEQ ID NO. 6) have been selected for further characterization. The humanized VH region in these constructs contain the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7. The corresponding amino acid sequences of the scFvs are shown in Table 1. Periplasmic extracts of said humanized constructs MP510-A5, MP511-B9, MP511-D8 as well as the half human construct A-240 Vlambda.3 (murine VH A5B7/human VL A240) were further analyzed in flow cytometric experiments with CEA-positive and -negative cell lines. It can be seen from FIG. 3, that the humanized constructs MP510-A5 (SEQ ID NO. 2), MP511-B9 (SEQ ID NO. 4), MP511-D8 (SEQ ID NO. 6) show clearly discernable shifts in fluorescence intensity as compared to the respective half-human control A-240 Vlambda.3 (murine VH A5B7/human VL A240). Thus, the human scFv constructs show stronger binding activity to membrane-bound human CEA than the half human construct A-240 Vlambda.3. In addition, all of the human constructs showed distinct binding to CEA-positive human KATO III cells (human gastric cancer cell line), whereas none of them showed binding to CEA-negative, untransfected CHO cells as well as to CEA-negative human NALM 6 cells (human B cell line) (data not shown).

EXAMPLE 5 Generation and Characterization of Humanized IgG1 Antibodies with Resistance to Soluble CEA Antigen

Although bacteria are known to express functional Fab fragments, they are usually not capable of producing complete functional immunoglobulins. For the production of complete functional IgG1 antibodies, mammalian cells must be used and therefore the VL region of scFv A-240 and different VH regions of scFv molecules selected in Example 4 (especially VH regions of scFv A5, scFv D8 and scFv B9) were subcloned into mammalian expression vectors.

1. Cloning of the Human Light Chain Based on scFv A-240

The human VL of clone A-240 contained a Bsu36I restriction site in its nucleotide sequence. Therefore a variant was generated (A-240delBsu) using standard protocols that had a nucleotide exchange in the restriction motif that did not result in an amino acid exchange.

For cloning of the VL A-240 into a suitable mammalian expression vector, suitable terminal restriction sites had to be inserted. Therefore the DNA fragment encoding the VL region of scFv A240 was reamplified by PCR using the primers 5′-A240-Bsu36I (TTCTCTCCTTAGGTGTCCACTCC CAG GCC GTG CTG ACT CAG CCG GC) (SEQ ID NO. 93) and 3′-A240-overlap (GCCTTGGGCTGACCTAGGACGGTC AACTTGGTCC) (SEQ ID NO. 94).

In a second PCR a human lambda constant region was amplified from a human cDNA pool using the 5′-primer 5′—Clam-overlap (GTTGACCGTCCTAGGTCAGCCCGGCTGCCCCCTCG) (SEQ ID NO. 95) and the 3′-primer 3′—Clam-NotI (GACGTA GCGGCCGC GTCGAC CTATGCATTCTGTAGGGGC) (SEQ ID NO. 96) according to standard methods. The approximately 330 bp DNA products of both PCRs had an identical 3′ (A-240) or 5′ (C lambda) overlap in sequence.

The two fragments were used in a fusion PCR (according to standard protocols) in combination with the 5′-primer 5′-A240-Bsu36I and the 3′-primer 3′—Clam-NotI to generate a full length light chain product coding for the human VL A-240 fused to a human lambda constant region (corresponding amino acid sequence shown in SEQ ID NO: 80). This DNA-fragment contained a Bsu36I-site at the 5′-end and a SalI restriction site at the 3′-terminus followed by a NotI restriction site. This fragment was then subcloned into the pBS-derived plasmid (as described above) by Bsu36I and Not I thus adding a human leader sequence. This construct was verified by sequencing. Utilizing EcoRI and SalI, A-240 VL-Clambda DNA was excised from said construct and subcloned into the eukaryotic expression vector pEF-ADA derived from the expression vector pEF-DHFR (Mack et al. (1995) Proc. Natl. Acad. Sci. USA. 92, 7021-5) by replacing the cDNA encoding murine dihydrofolate reductase (DHFR) with that encoding murine adenosine deaminase (ADA). pEF-ADA is described in Raum, loc. cit. The amino acid sequence of A-240 VL-Clambda (corresponding to the A240 light chain) is shown in SEQ ID NO. 80.

2. Cloning of Humanized Heavy Chain Variable Domains

From different humanized VH regions selected in example 4 (especially VH regions of scFv A5, scFv D8 and scFv B9), the variable region was reamplified by PCR, generating Bsu36I restriction sites at both ends. For all constructs the combination of two primers was used: 5′-primer 5′-CVH-Bsu36I (5′-TTCTCTCCTTAGGTGTCCACTCC GAG GTG CAG CTG GTC GAG TC-3′) (SEQ ID NO. 97) and 3′-primer 3′-CVH-Bsu36I (5′-GACTCACCTGAGGA GAC GGT GAC CGT GGT CCC TTG G-3′) (SEQ ID NO. 98). The resulting DNA-fragments were then subcloned using these restriction sites into the eukaryotic expression vector pEF-DHFR already containing a eukaryotic leader sequence and a DNA-fragment encoding the human IgG1 heavy chain constant region. The heavy chain variable regions were thus inserted between the leader and the heavy chain constant region. The correct sequences of the variable regions were confirmed by sequencing. The amino acid sequence of the A5 heavy chain is shown in SEQ ID NO. 77, the amino acid sequence of the B9 heavy chain is shown in SEQ ID NO. 78 and the amino acid sequence of the D8 heavy chain is shown in SEQ ID NO. 79.

3. Expression of Humanized Full IgG Proteins

Plasmid encoding for one light chain and plasmid encoding for one heavy chain (VH/human IgG1 constant region) were cotransfected into HEK cells according to standard protocols for transient protein expression and the cells were cultured to allow the expression and production of the immunoglobulins into the culture medium. In this manner, IgG1 A5 derived from scFv A5, IgG1 D8 derived from scFv D8 and IgG1 B9 derived from scFv B9 were produced. After the respective production period, the supernatants were harvested and the humanized immunoglobulins were isolated via Protein A chromatography according to standard protocols for the purification of immunoglobulins. Culture supernatants, as well as purified immunoglobulins were then used for further characterization experiments.

The amino acid sequence of the A5 heavy chain is shown in SEQ ID NO. 77, the amino acid sequence of the B9 heavy chain is shown in SEQ ID NO. 78 and the amino acid sequence of the D8 heavy chain is shown in SEQ ID NO. 79. The amino acid sequence of the A240 light chain is shown in SEQ ID NO. 80.

IgG1 A5, derived from scFv A5, comprises the A5 heavy chain shown in SEQ ID NO. 77 and the amino acid sequence of the A240 light chain shown in SEQ ID NO. 80. IgG1 B9, derived from scFv B9, comprises the amino acid sequence of the B9 heavy chain shown in SEQ ID NO. 78 and the amino acid sequence of the A240 light chain shown in SEQ ID NO. 80. IgG1 D8, derived from scFv D8, comprises the amino acid sequence of the D8 heavy chain shown in SEQ ID NO. 79 and the amino acid sequence of the A240 light chain shown in SEQ ID NO. 80. The (humanized) VH region in these IgG1 antibody constructs contains the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7. The corresponding amino acid sequences of the above mentioned heavy and light chains are shown in Table 1.

4. Characterization of Humanized IgG1 Antibodies with Resistance to Soluble CEA Antigen 4.1 Binding to Immobilized Soluble CEA (sCEA) Antigen

Culture supernatants of heavy+light chain double transfectants as well as the corresponding preparations of purified antibody were tested for binding on immobilized sCEA antigen by ELISA according to standard procedures. An irrelevant human IgG1 antibody was included as a negative control.

In brief, antibody binding was tested on immobilized CEA antigen and for demonstration of CEA specificity also in the absence of coated CEA antigen using culture supernatant and purified antibody solutions of 10 ug/ml and 1 ug/ml, respectively. These antibody solutions were added to the +/−antigen coated (4° C. over night) and BSA blocked wells (1 hr, 37° C.). Detection was performed by peroxidase-labeled polyclonal human IgG antibody (Jackson ImmunoResearch). The signals were measured after appropriate incubation with ABTS solution.

As shown in FIG. 4, the humanized antibodies IgG1 A5, IgG1 D8 and IgG1 B9 as well as the huIgG1-CEA I and —CEA II constructs of Example 2 showed distinct binding to the immobilized soluble CEA (sCEA) antigen as compared to the negative control—and no binding in an equivalent setting with the difference that no sCEA antigen was coated.

4.2 Binding to Native CEA Antigen on Cells

Purified antibody preparations of humanized IgG1 A5, IgG1 D8 and IgG1 B9 constructs as well as the huIgG1-CEA I and —CEA II constructs of Example 2 were tested by FACS analysis on CEA expressing Kato III cells, CEA-transfected CHO-cells and CEA-untransfected CHO-cells.

2×10⁵ cells were incubated with purified antibody preparations (typically 10-20 μg/ml). Detection was performed by a biotinylated polyclonal anti-human IgG antibody (DAKO) followed by PE-labeled Streptavidine (Jackson ImmunoResearch) (typically 10-20 μg/ml). Incubation was carried out for 20-40 min. on ice.

The humanized IgG1 A5, IgG1 D8 and IgG1 B9 constructs as well as the huIgG-CEA I and —CEA II constructs of Example 2 showed distinct binding to the CEA positive cells (FIGS. 5A, B and C). None of the antibodies showed binding to untransfected CHO cells. IgG-controls were negative on Kato-cells, CHO/CEA-cells and untransfected CHO cells.

4.3 Antibody Dependent Cell-Mediated Cytotoxicity (ADCC; ⁵¹Cr Release Assay)

For the ⁵¹Cr release assay, human peripheral blood mononuclear cells (PBMCs) as effector cells were isolated from a healthy donors. The PBMCs were separated by Ficoll density gradient centrifugation with a subsequent 100×g centrifugation step. Unstimulated PBMCs (5×10⁵ cells) were added in a volume of 100 μl of RPMI 1640 medium with 10% FCS to each well of a flat bottomed microtiter plate and incubated overnight at 37° C. As target cells, the CEA-positive gastric cancer cell line KATO III has been used. Target cells (50.000 cells) were labelled for 2 h with ⁵¹Cr. Labeled target cells (100 μl) and antibodies in different concentrations (10 μg/ml-10 μg/ml) were added to the PBMCs and incubated for 18 h at 37° C. Corresponding non-binding isotypes were used as negative controls. Specific lysis was calculated as ((cpm, experimental release)−(cpm, spontaneous release))/((cpm, maximal release)−(cpm, spontaneous release)).

In the absence of sCEA, the humanized anti-CEA antibodies IgG1 A5, IgG1 D8 and IgG1 B9 proved to mediate cytotoxicity to the CEA positive gastric cancer cell line KATO III as compared to the negative control. The same result has been observed for the IgG versions of the antibodies CEA I and CEA II (huIgG1-CEA I and —CEA II constructs) as set forth in Example 2. In parallel, the antibody samples were preincubated with soluble CEA (sCEA) antigen for 20 min under agitation and then mixed with the labeled target cells and the human PBMCs. Otherwise, the assay has been performed as described above. Soluble CEA (sCEA) antigen has been used in different concentrations, i.e. 1 μg/ml and 10 μg/ml. The assay was measured and the respective cytotoxic values plotted.

Two representative results are shown in FIGS. 6 A and B for antibody CEA II and antibody IgG1 A5, respectively. It was demonstrated in this assay that the cytolytic potential of antibody CEA II was dramatically reduced in the presence of soluble CEA antigen in a dose-dependent manner. The respective curve clearly shifts to the right in the presence of 1 ug/ml sCEA as compared to the curve without soluble CEA. In the presence of 10 ug/ml sCEA, no cytolytic curve was observed indicating the complete reduction of cytolytic activity of antibody CEA II below detection level. The respective EC 50 values (half maximal cytolytic antibody concentrations) were estimated as being higher in concentration than the last cytotoxic value at base level. This leads to an underestimation of the EC50 levels for antibody CEA II and a probably even much higher “inhibitory factor” as specified below.

In contrast, no significant inhibitory effect of soluble CEA antigen in the cytolytic assay was demonstrated for the antibodies IgG1 A5, IgG1 B9 and IgG1 D8. All antibodies showed comparable EC50 values in the absence of soluble CEA, indicating a comparable cytolytic activity in the absence of soluble CEA.

EC50 values were determined by the analysis software. The EC 50 values are depicted in Table 2.

TABLE 2 ADCC EC50 values of the respective antibodies in ng/ml in the presence of different concentrations of soluble CEA (sCEA) sCEA ug/ml CEA II IgG1 A5 IgG1 B9 IgG1 D8 0 2.7 2.7 4.8 4.4 1 >100 4 45.3 14.7 10 >200 2.8 53.4 6.3

Cytolytic inhibition in the presence of soluble CEA antigen was converted into an “inhibitory factor”. This factor is defined as the EC50 in the presence of 10 and 1 ug/ml soluble CEA in the ADCC assay divided by the EC50 in absence of soluble CEA. The inhibitory factors are depicted in Table 3.

TABLE 3 Inhibitory factors of the respective antibodies in the presence of different concentrations of soluble CEA (sCEA) CEA II IgG1 A5 IgG1 B9 IgG1 D8 10 ug/ml sCEA >74.1 1.0 11.1 1.4  1 ug/ml sCEA >37.0 1.5 9.4 3.3

A graphic presentation of the inhibitory factors is illustrated in FIG. 7. This Figure shows clearly, that CEA II has a dramatically decreased cytolytic activity in the presence of soluble CEA antigen at 1 ug/ml, showing a more than 37 times reduced cytolytic activity in the presence of soluble CEA antigen, whereas IgG1 A5- and IgG1 D8-mediated cytolytic activity towards tumor cells is completely resistant to soluble CEA. IgG1 B9-mediated cytolytic activity towards tumor cells is only slightly affected by sCEA. Said antibody constructs show inhibitory factors below 10.

This effect is even more pronounced at the 10 ug/ml concentration of soluble CEA in the ADCC assay. The cytolytic curve of antibody CEA II is reduced to baseline (no cytolytic activity even at the highest concentrations could be detected). Therefore the inhibitory factor for antibody CEA II was estimated to be 74 at it's best, probably being far underestimated.

In summary, in the presence of soluble CEA, huIgG-CEA II (derived from mAb T84.66) showed drastically reduced cytotoxic activity against CEA positive target cells; see Examples 2 and 5. In contrast, the humanized CEA antibodies IgG1 A5, IgG1 D8 and IgG1 B9 showed no significant decrease of cytolytic activity as compared to the activity in the absence of soluble CEA. IgG1 A5-, IgG1 B9- and IgG1 D8-mediated cytolytic activity towards tumor cells is resistant to soluble CEA. Surprisingly, the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) corresponding to Kabat positions 95-102 of the CDR-H3 of murine monoclonal antibody A5B7 in the VH regions of the otherwise completely human IgG1 antibodies IgG1 A5, IgG1 D8 and IgG1 B9 is sufficient to mediate resistance to soluble CEA antigen.

TABLE 1 SEQ ID NO. SOURCE SEQUENCE 1 A5 VH −A240VL human Nt GAGGTGCAGCTGCTCGAGTCTGGGGGAGGCGTGGTCCAGCCTGGGAGGTCCCTGAGACTC TCCTGTGCAGCCTCTGGATTCACCCTCAGTACCTATGCCATGCACTGGGTCCGCCAGGCT CCAGGCAAGGGGCTGGAGTGGGTGGCACTTATATCAAATGATGGAAGCAATAAATACTAT GCAGACTCCGTGAAGGGCCGATTCACCATCTCCAGAGACAATTCCAAGAACACGCTGTAT CTGCAAATGAACAGCCTGAGAGCTGAGGACACGGCCGTGTATTACTGTGCGAGAGATAGG GGGCTACGGTTCTACTTTGACTACTGGGGCCAAGGGACCACGGTCACCGTCTCCTCAGGT GGTGGTGGTTCTGGCGGCGGCGGCTCCGGTGGTGGTGGTTCTGAGCTCGTGCTGACTCAG CCGGCTTCCCTCTCTGCATCTCCTGGAGCATCAGCCAGTCTCACCTGCACCTTGCGCAGG GGCATCAATGTTGGTGCCTACAGTATATACTGGTACCAGCAGAAGCCAGGGAGTCCTCCC CAGTATCTCCTGAGGTACAAATCAGACTCAGATAAGCAGCAGGGCTCTGGAGTCTCCAGC CGCTTCTCTGCATCCAAAGATGCTTCGGCCAATGCAGGGATTTTACTCATCTCTGGGCTC CAGTCTGAGGATGAGGCTGACTATTACTGTATGATTTGGCACAGCGGCGCTTCTGCGGTG TTCGGCGGAGGGACCAAGTTGACCGTCCTATAG 2 A5 VH −A240VL human AA EVQLLESGGGVVQPGRSLRLSCAASGFTLSTYAMHWVRQAPGKGLEWVALISNDGSNKYY ADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARDRGLRFYFDYWGQGTTVTVSSG GGGSGGGGSGGGGSELVLTQPASLSASPGASASLTCTLRRGINVGAYSIYWYQQKPGSPP QYLLRYKSDSDKQQGSGVSSRFSASKDASANAGILLISGLQSEDEADYYCMIWHSGASAV FGGGTKLTVL* 3 B9 VH −A240VL human Nt GAGGTGCAGCTGCTCGAGTCTGGGGGAGGCTTGGTCCAGCCTGGGAGGTCCCTGAGACTC TCCTGTGCAGCGTCTGGATTCACCGTCAGTAGCTACTGGATGCACTGGGTCCGCCAAGCT CCAGGGAAGGGGCTGGAATGGGTAGGTTTCATTAGAAACAAAGCTAATGGTGGGACAACA GAATACGCCGCGTCTGTGAAAGGCAGATTCACCATCTCAAGAGATGATTCCAAGAACACG CTGTATCTTCAAATGAACAGCCTGAGAGCCGAGGACACGGCCGTGTATTACTGTGCAAGA GATAGGGGGCTACGGTTCTACTTTGACTACTGGGGCCAAGGGACCACGGTCACCGTCTCC TCAGGTGGTGGTGGTTCTGGCGGCGGCGGCTCCGGTGGTGGTGGTTCTGAGCTCGTGCTG ACTCAGCCGGCTTCCCTCTCTGCATCTCCTGGAGCATCAGCCAGTCTCACCTGCACCTTG CGCAGGGGCATCAATGTTGGTGCCTACAGTATATACTGGTACCAGCAGAAGCCAGGGAGT CCTCCCCAGTATCTCCTGAGGTACAAATCAGACTCAGATAAGCAGCAGGGCTCTGGAGTC TCCAGCCGCTTCTCTGCATCCAAAGATGCTTCGGCCAATGCAGGGATTTTACTCATCTCT GGGCTCCAGTCTGAGGATGAGGCTGACTATTACTGTATGATTTGGCACAGCGGCGCTTCT GCGGTGTTCGGCGGAGGGACCAAGTTGACCGTCCTATAG 4 B9 VH −A240VL human AA EVQLLESGGGLVQPGRSLRLSCAASGFTVSSYWMHWVRQAPGKGLEWVGFIRNKANGGTT EYAASVKGRFTISRDDSKNTLYLQMNSLRAEDTAVYYCARDRGLRFYFDYWGQGTTVTVS SGGGGSGGGGSGGGGSELVLTQPASLSASPGASASLTCTLRRGINVGAYSIYWYQQKPGS PPQYLLRYKSDSDKQQGSGVSSRFSASKDASANAGILLISGLQSEDEADYYCMIWHSGAS AVFGGGTKLTVL* 5 D8 VH −A240VL human Nt GAGGTGCAGCTGCTCGAGTCTGGGGGAGGCGTGGTCCAGCCTGGGAGGTCCCTGAGACTC TCCTGTGCAGCCTCTGGATTCACCCTCAGTACCTATGCCATGCACTGGGTCCGCCAGGCT CCAGGCAAGGGGCTGGAGTGGGTGGCACTTATATCAAATGATGGAAGCAATAAATACTAT GCAGACTCCGTGAAGGGCCGATTCACCATCTCCAGAGACAATTCCAAGAACACGCTGTAT CTGCAAATGAACAGCCTGAGAGCTGAGGACACGGCTGTGTATTACTGTACTAGAGATAGG GGGCTACGGTTCTACTTTGACTACTGGGGCCAAGGGACCACGGTCACCGTCTCCTCAGGT GGTGGTGGTTCTGGCGGCGGCGGCTCCGGTGGTGGTGGTTCTGAGCTCGTGCTGACTCAG CCGGCTTCCCTCTCTGCATCTCCTGGAGCATCAGCCAGTCTCACCTGCACCTTGCGCAGG GGCATCAATGTTGGTGCCTACAGTATATACTGGTACCAGCAGAAGCCAGGGAGTCCTCCC CAGTATCTCCTGAGGTACAAATCAGACTCAGATAAGCAGCAGGGCTCTGGAGTCTCCAGC CGCTTCTCTGCATCCAAAGATGCTTCGGCCAATGCAGGGATTTTACTCATCTCTGGGCTC CAGTCTGAGGATGAGGCTGACTATTACTGTATGATTTGGCACAGCGGCGCTTCTGCGGTG TTCGGCGGAGGGACCAAGTTGACCGTCCTATAG 6 D8 VH −A240VL human AA EVQLLESGGGVVQPGRSLRLSCAASGFTLSTYAMHWVRQAPGKGLEWVALISNDGSNKYY ADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCTRDRGLRFYFDYWGQGTTVTVSSG GGGSGGGGSGGGGSELVLTQPASLSASPGASASLTCTLRRGINVGAYSIYWYQQKPGSPP QYLLRYKSDSDKQQGSGVSSRFSASKDASANAGILLISGLQSEDEADYYCMIWHSGASAV FGGGTKLTVL* 7 A5B7 VH murine Nt GAGGTGCAGCTGGTCGAGTCAGGAGGAGGCTTGGTACAGCCTGGGGGTTCTCTGAGACTC TCCTGTGCAACTTCTGGGTTCACCTTCACTGATTACTACATGAACTGGGTCCGCCAGCCT CCAGGAAAGGCACTTGAGTGGTTGGGTTTTATTGGAAACAAAGCTAATGGTTACACAACA GAGTACAGTGCATCTGTGAAGGGTCGGTTCACCATCTCCAGAGATAAATCCCAAAGCATC CTCTATCTTCAAATGAACACCCTGAGAGCTGAGGACAGTGCCACTTATTACTGTACCAGA GATAGGGGGCTACGGTTCTACTTTGACTACTGGGGCCAAGGGACCACGGTCACCGTCTCC TCA 8 A5B7 VH murine AA EVQLVESGGGLVQPGGSLRLSCATSGFTFTDYYMNWVRQPPGKALEWLGFIGNKANGYTT EYSASVKGRFTISRDKSQSILYLQMNTLRAEDSATYYCTRDRGLRFYFDYWGQGTTVTV SS 9 A5B7 VL murine Nt GACATTGAGCTCACCCAGTCTCCAGCAATCCTGTCTGCATCTCCAGGGGAGAAGGTCACA ATGACTTGCAGGGCCAGCTCAAGTGTAACTTACATTCACTGGTACCAGCAGAAGCCAGGA TCCTCCCCCAAATCCTGGATTTATGCCACATCCAACCTGGCTTCTGGAGTCCCTGCTCGC TTCAGTGGCAGTGGGTCTGGGACCTCTTACTCTCTCACAATCAGCAGAGTGGAGGCTGAA GATGCTGCCACTTATTACTGCCAACATTGGAGTAGTAAACCACCGACGTTCGGTGGAGGG ACCAAGCTCGAGATCAAA 10 A5B7 VL murine AA DIELTQSPAILSASPGEKVTMTCRASSSVTYIHWYQQKPGSSPKSWIYATSNLASGVPAR FSGSGSGTSYSLTISRVEAEDAATYYCQHWSSKPPTFGGGTKLEIK 11 T84.66 VH murine Nt GAGGTTCAGCTGCAGCAGTCTGGGGCAGAGCTTGTGGAGCCAGGGGCCTCAGTCAAGTTG TCCTGCACAGCTTCTGGCTTCAACATTAAAGACACCTATATGCACTGGGTGAAGCAGAGG CCTGAACAGGGCCTGGAATGGATTGGAAGGATTGATCCTGCGAATGGTAATAGTAAATAT GTCCCGAAGTTCCAGGGCAAGGCCACTATAACAGCAGACACATCCTCCAACACAGCCTAC CTGCAGCTCACCAGCCTGACATCTGAGGACACTGCCGTCTATTATTGTGCTCCGTTTGGT TACTACGTGTCTGACTATGCTATGGCCTACTGGGGTCAAGGAACCTCAGTCACCGTCTCC TCC 12 T84.66 VH murine AA EVQLQQSGAELVEPGASVKLSCTASGFNIKDTYMHWVKQRPEQGLEWIGRIDPANGNSKY VPKFQGKATITADTSSNTAYLQLTSLTSEDTAVYYCAPFGYYVSDYAMAYWGQGTSVTV SS 13 T84.66 VL murine Nt GACATTGTGCTGACCCAATCTCCAGCTTCTTTGGCTGTGTCTCTTGGGCAGAGGGCCACC ATGTCCTGCAGAGCCGGTGAAAGTGTTGATATTTTTGGCGTTGGGTTTTTGCACTGGTAC CAGCAGAAACCAGGACAGCCACCCAAACTCCTCATCTATCGTGCATCCAACCTAGAATCT GGGATCCCTGTCAGGTTCAGTGGCACTGGGTCTAGGACAGACTTCACCCTCATCATTGAT CCTGTGGAGGCTGATGATGTTGCCACCTATTACTGTCAGCAAACTAATGAGGATCCGTAC ACGTTCGGAGGGGGGACCAAGCTCGAGATAAAA 14 T84.66 VL murine AA DIVLTQSPASLAVSLGQRATMSCRAGESVDIFGVGFLHWYQQKPGQPPKLLIYRASNLES GIPVRFSGTGSRTDFTLIIDPVEADDVATYYCQQTNEDPYTFGGGTKLEIK 15 MFE-23 VH murine Nt CAGGTTAAGCTGCAGCAGTCTGGGGCAGAGCTTGTGAGATCAGGGACATCAGTCAAGTTG TCCTGCACAGCTTCTGGCTTCAACATTAAAGACTCCTATATGCACTGGCTGAGGCAGGGG CCTGAACAGGGCCTGGAGTGGATTGGATGGATTGATCCTGAGAATGGTGATACTGAATAT GCCCCGAAGTTCCAGGGCAAGGCCACTTTCACTACTGACACATCCTCCAACACAGCCTAC CTGCAGCTCAGCAGCCTGACATCTGAGGACACTGCCGTCTATTACTGTAACGAGGGCACA CCTACAGGGCCTTACTACTTTGACTACTGGGGCCAAGGCACCACTGTCACAGTCTCCTCC 16 MFE-23 VH murine AA QVKLQQSGAELVRSGTSVKLSCTASGFNIKDSYMHWLRQGPEQGLEWIGWIDPENGDTEY APKFQGKATFTTDTSSNTAYLQLSSLTSEDTAVYYCNEGTPTGPYYFDYWGQGTTVTVSS 17 MFE-23 VL murine Nt GAGAACGTTCTCACCCAGTCTCCAGCAATCATGTCTGCATCTCCAGGGGAGAAGGTCACC ATCACCTGCAGTGCCAGCTCAAGCGTCAGCTACATGCACTGGTTCCAGCAGAAGCCAGGC ACCTCCCCCAAACTCTGGATTTATTCTACATCCAACCTGGCTTCTGGAGTCCCTGCTCGC TTCTCTGGCAGTGGGTCTGGGACCTCTTACTCTCTCACAATCAGCAGAATGGAGGCTGAA GATGCTGCCACTTATTACTGCCAGCAGAGAAGTAGTTACCCACTCACGTTCGGTGCTGGG ACCAAGCTCGAGCTGAAA 18 MFE-23 VL murine AA ENVLTQSPAIMSASPGEKVTITCSASSSVSYMHWFQQKPGTSPKLWIYSTSNLASGVPAR FSGSGSGTSYSLTISRMEAEDAATYYCQQRSSYPLTFGAGTKLELK 19 A5 VH human Nt GAGGTGCAGCTGGTCGAGTCTGGGGGAGGCGTGGTCCAGCCTGGGAGGTCCCTGAGACTC TCCTGTGCAGCCTCTGGATTCACCCTCAGTACCTATGCCATGCACTGGGTCCGCCAGGCT CCAGGCAAGGGGCTGGAGTGGGTGGCACTTATATCAAATGATGGAAGCAATAAATACTAT GCAGACTCCGTGAAGGGCCGATTCACCATCTCCAGAGACAATTCCAAGAACACGCTGTAT CTGCAAATGAACAGCCTGAGAGCTGAGGACACGGCCGTGTATTACTGTGCGAGAGATAGG GGGCTACGGTTCTACTTTGACTACTGGGGCCAAGGGACCACGGTCACCGTCTCCTCA 20 A5 VH human AA EVQLVESGGGVVQPGRSLRLSCAASGFTLSTYAMHWVRQAPGKGLEWVALISNDGSNKYY ADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARDRGLRFYFDYWGQGTTVTVSS 21 B9 VH human Nt GAGGTGCAGCTGGTCGAGTCTGGGGGAGGCTTGGTCCAGCCTGGGAGGTCCCTGAGACTC TCCTGTGCAGCGTCTGGATTCACCGTCAGTAGCTACTGGATGCACTGGGTCCGCCAAGCT CCAGGGAAGGGGCTGGAATGGGTAGGTTTCATTAGAAACAAAGCTAATGGTGGGACAACA GAATACGCCGCGTCTGTGAAAGGCAGATTCACCATCTCAAGAGATGATTCCAAGAACACG CTGTATCTTCAAATGAACAGCCTGAGAGCCGAGGACACGGCCGTGTATTACTGTGCAAGA GATAGGGGGCTACGGTTCTACTTTGACTACTGGGGCCAAGGGACCACGGTCACCGTCTCC TCA 22 B9 VH human AA EVQLVESGGGLVQPGRSLRLSCAASGFTVSSYWMHWVRQAPGKGLEWVGFIRNKANGGTT EYAASVKGRFTISRDDSKNTLYLQMNSLRAEDTAVYYCARDRGLRFYFDYWGQGTTVTV SS 23 D8 VH human Nt GAGGTGCAGCTGGTCGAGTCTGGGGGAGGCGTGGTCCAGCCTGGGAGGTCCCTGAGACTC TCCTGTGCAGCCTCTGGATTCACCCTCAGTACCTATGCCATGCACTGGGTCCGCCAGGCT CCAGGCAAGGGGCTGGAGTGGGTGGCACTTATATCAAATGATGGAAGCAATAAATACTAT GCAGACTCCGTGAAGGGCCGATTCACCATCTCCAGAGACAATTCCAAGAACACGCTGTAT CTGCAAATGAACAGCCTGAGAGCTGAGGACACGGCTGTGTATTACTGTACTAGAGATAGG GGGCTACGGTTCTACTTTGACTACTGGGGCCAAGGGACCACGGTCACCGTCTCCTCA 24 D8 VH human AA EVQLVESGGGVVQPGRSLRLSCAASGFTLSTYAMHWVRQAPGKGLEWVALISNDGSNKYY ADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCTRDRGLRFYFDYWGQGTTVTVSS 25 A240VL human Nt CAGGCCGTGCTGACTCAGCCGGCTTCCCTCTCTGCATCTCCTGGAGCATCAGCCAGTCTC ACCTGCACCTTGCGCAGGGGCATCAATGTTGGTGCCTACAGTATATACTGGTACCAGCAG AAGCCAGGGAGTCCTCCCCAGTATCTCCTGAGGTACAAATCAGACTCAGATAAGCAGCAG GGCTCTGGAGTCTCCAGCCGCTTCTCTGCATCCAAAGATGCTTCGGCCAATGCAGGGATT TTACTCATCTCTGGGCTCCAGTCTGAGGATGAGGCTGACTATTACTGTATGATTTGGCAC AGCGGCGCTTCTGCGGTGTTCGGCGGAGGGACCAAGTTGACCGTCCTA 26 A240VL human AA QAVLTQPASLSASPGASASLTCTLRRGINVGAYSIYWYQQKPGSPPQYLLRYKSDSDKQQ GSGVSSRFSASKDASANAGILLISGLQSEDEADYYCMIWHSGASAVFGGGTKLTVL 27 CDR-H3 A5B7 murine AA DRGLRFYFDY Kabat positions 95, 96, 97, 98, 99, 100, 100a, 100b, 101, 102 28 CDR-H2 B9 human AA FIRNKANGGTTEYAASVKG 29 CDR-H1 B9 human AA SYWMH 30 CDR-H2 A5/D8 human AA LISNDGSNKYYADSVKG 31 CDR-H1 A5/D8 human AA TYAMH 32 CDR-L3 A240 human AA MIWHSGASAV 33 CDR-L2 A240 human AA YKSDSDKQQGS 34 CDR-L1 A240 human AA TLRRGINVGAYSIY 35 5′ CEACAM5 EcoRI artificial Nt GAATTCGCCACCATGGAGTCTCCCTCGGCCCC 36 3′ CEACAM5 artificial Nt GTCGACCTATATCAGAGCAACCCC Sal I 37 CEACAM5 human AA MESPSAPPHRWCIPWQRLLLTASLLTFWNPPTTAKLTIESTPFN (NM_004363) VAEGKEVLLLVHNLPQHLFGYSWYKGERVDGNRQIIGYVIGTQQATPGPAYSGREIIY PNASLLIQNIIQNDTGFYTLHVIKSDLVNEEATGQFRVYPELPKPSISSNNSKPVEDK DAVAFTCEPETQDATYLWWVNNQSLPVSPRLQLSNGNRTLTLFNVTRNDTASYKCETQ NPVSARRSDSVILNVLYGPDAPTISPLNTSYRSGENLNLSCHAASNPPAQYSWFVNGT FQQSTQELFIPNITVNNSGSYTCQAHNSDTGLNRTTVTTITVYAEPPKPFITSNNSNP VEDEDAVALTCEPEIQNTTYLWWVNNQSLPVSPRLQLSNDNRTLTLLSVTRNDVGPYE CGIQNELSVDHSDPVILNVLYGPDDPTISPSYTYYRPGVNLSLSCHAASNPPAQYSWL IDGNIQQHTQELFISNITEKNSGLYTCQANNSASGHSRTTVKTITVSAELPKPSISSN NSKPVEDKDAVAFTCEPEAQNTTYLWWVNGQSLPVSPRLQLSNGNRTLTLFNVTRNDA RAYVCGIQNSVSANRSDPVTLDVLYGPDTPIISPPDSSYLSGANLNLSCHSASNPSPQ YSWRINGIPQQHTQVLFIAKITPNNNGTYACFVSNLATGRNNSIVKSITVSASGTSPG LSAGATVGIMIGVLVGVALI 38 5′-huVK1-SacI- artificial Nt GAGCCGCACG AGCCCGAGCT CCAGATGACC CAGTCTCC 2001 39 5′-huVK2/4-SacI- artificial Nt GAGCCGCACG AGCCCGAGCT CGTGATGACY CAGTCTCC 2001 40 5′-huVK3-SacI- artificial Nt GAGCCGCACG AGCCCGAGCT CGTGWTGACR CAGTCTCC 2001 41 5′-huVK5-SacI- artificial Nt GAGCCGCACG AGCCCGAGCT CACACTCACG CAGTCTCC 2001 42 5′-huVK6-SacI- artificial Nt GAGCCGCACG AGCCCGAGCT CGTGCTGACT CAGTCTCC 2001 43 3′-hu-Vk-J1-SpeI- artificial Nt GACGACACTA GTTGCAGCCA CCGTACGTTT GATTTCCACC TTGGTCC BsiWI 44 3′-hu-Vk-J2/4-SpeI- artificial Nt GACGACACTA GTTGCAGCCA CCGTACGTTT GATCTCCASC TTGGTCC BsiWI 45 3′-hu-Vk-J3-SpeI- artificial Nt GACGACACTA GTTGCAGCCA CCGTACGTTT GATATCCACT TTGGTCC BsiWI 46 3′-hu-Vk-J5-SpeI- artificial Nt GACGACACTA GTTGCAGCCA CCGTACGTTT AATCTCCAGT CGTGTCC BsiWI 47 5′-huVL1a-SacI-2001 artificial Nt GAG CCG CAC GAG CCC GAG CTC GTG TTG ACG CAG CCG CCC TC 48 5′-huVL1b-SacI-2001 artificial Nt GAG CCG CAC GAG CCC GAG CTC GTG CTG ACT CAG CCA CCC TC 49 5′-huVL2-SacI-2001 artificial Nt GAG CCG CAG GAG CCC GAG CTC GCC CTG ACT CAG CCT SCC TCC GT 50 5′-huVL4-SacI-2001 artificial Nt ACC TGC GAG CTC GTG CTG ACT CAR YCM YCC TCT GC 51 5′-huVL5-SacI-2001 artificial Nt ACC TGC GAG CTC GTG CTG ACT CAG CCR SCT TCC 52 5′-huVL6-SacI-2001 artificial Nt ACC TGC GAG CTC ATG CTG ACT CAG CCC CAC TC 53 5′-huVL3/9-SacI- artificial Nt GAG CCG CAC GAG CCC GAG CTC GWG CTG ACT CAG CCA CCY TC 2001 54 5′-huVL7/8-SacI- artificial Nt GAG CCG CAC GAG CCC GAG CTC GTG GTG AGY CAG GAG CCM TC 2001 55 3′-hu-Vlam-BlnI- artificial Nt CGT GGG ACT AGT CTT GGG CTG ACC TAG GAC GGT SpeI-2001 56 3′-hu-Vlam2-BlnI- artificial Nt CGT GGG ACT AGT CTT GGG CTG ACC GAG GAC GGT SpeI-2002 57 5′-primer 5′-AVH- artificial Nt GTC ACA CTC GAG TCA GGA GGA GGC TTG GTA C XhoI 58 3′-primer 3′-AVH- artificial Nt GTC ACA GGT GAC CGT GGT CCC TTG GCC CCA G BstEII 59 Flag tag artificial AA TGDYKDDDDK 60 5′-huVH1,3,5-XhoI- artificial Nt AGG TGC AGC TGC TCG AGT CTG G 2001 61 5′-huVH4-XhoI-2001 artificial Nt CAG GTG CAG CTG CTC GAG TCG GG 62 5′-huVH4B-XhoI- artificial Nt CAG GTG CAG CTA CTC GAG TGG GG 2001 63 3′-hu-VH-BstEII- artificial Nt CTG AGG AGA CGG TGA CC 2001 64 3′-hu-VH-J3-BstEII- artificial Nt CTG AAG AGA CGG TGA CC 2001 65 3′-A134-VH1A artificial Nt GTA GTC AAA GTA GAA CCG TAG CCC CCT ATC TCT YGC ACA GTA ATA CAC GGC 66 3′-A134-VH1B artificial Nt GTA GTC AAA GTA GAA CCG TAG CCC CCT ATC TCT YGC ACA GTA ATA CAY RGC 67 3′-A134-VH3A artificial Nt GTA GTC AAA GTA GAA CCG TAG CCC CCT ATC TCT NGY ACA GTA ATA CAC RGC 68 3′-A134-VH3B artificial Nt GTA GTC AAA GTA GAA CCG TAG CCC CCT ATC TCT NGC ACA GTA ATA CAA RGC 69 3′-A134-VH4 artificial Nt GTA GTC AAA GTA GAA CCG TAG CCC CCT ATC TCT SGC ACA GTA ATA CAC RGC 70 3′ A134-JH6-BstEII, artificial Nt CGA GAC GGT GAC CGT GGT CCC TTG GCC CCA GTA GTC AAA GTA GAA CCG TAG CC 71 A5B7 HC murine AA EVQLVESGGGLVQPGGSLRLSCATSGFTFTDYYMNWVRQPPGKALEWLGFIGNKANGYTT EYSASVKGRFTISRDKSQSILYLQMNTLRAEDSATYYCTRDRGLRFYFDYWGQGTTVTVS SASTKGPSVFPLAPSSKSTSGGTMLGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSS GLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGG PSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYN STYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDE LTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRW QQGNVFSCSVMHEALHNHYTQKSLSLSPGK 72 A5B7 LC murine AA DIELTQSPAILSASPGEKVTMTCRASSSVTYIHWYQQKPGSSPKSWIYATSNLASGVPAR FSGSGSGTSYSLTISRVEAEDAATYYCQHWSSKPPTFGGGTKLEIKRADAAPTVSIFPPS SEQLTSGGASVVCFLNNFYPKDINVKWKIDGSERQNGVLNSWTDQDSKDSTYSMSSTLTL TKDEYERHNSYTCEATHKTSTSPIVKSFNRNEC 73 T84.66 HC murine AA EVQLQQSGAELVEPGASVKLSCTASGFNIKDTYMHWVKQRPEQGLEWIGRIDPANGNSKY VPKFQGKATITADTSSNTAYLQLTSLTSEDTAVYYCAPFGYYVSDYAMAYWGQGTSVTVS SASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQS SGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLG GPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQY NSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRD ELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK 74 T84.66 LC murine AA DIVLTQSPASLAVSLGQRATMSCRAGESVDIFGVGFLHWYQQKPGQPPKLLIYRASNLES GIPVRFSGTGSRTDFTLIIDPVEADDVATYYCQQTNEDPYTFGGGTKLEIKRADAAPTVS IFPPSSEQLTSGGASVVFLNNFYPKDINVKWKIDGSERQNGVLNSWTDQDSKDSTYSMSS TLTLTKDEYERHNSYTCEATHKTSTSPIVKSFNRNEC 75 MFE-23 HC murine AA QVKLQQSGAELVRSGTSVKLSCTASGFNIKDSYMHWLRQGPEQGLEWIGWIDPENGDTEY APKFQGKATFTTDTSSNTAYLQLSSLTSEDTAVYYCNEGTPTGPYYFDYWGQGTTVTVSS ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSS GLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGG PSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYN STYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDE LTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRW QQGNVFSCSVMHEALHNHYTQKSLSLSPGK 76 MFE-23 LC murine AA ENVLTQSPAIMSASPGEKVTITCSASSSVSYMHWFQQKPGTSPKLWIYSTSNLASGVPAR FSGSGSGTSYSLTISRMEAEDAATYYCQQRSSYPLTFGAGTKLELKRADAAPTVSIFPPS SEQLTSGGASVVCFLNNFYPKDINVKWKIDGSERQNGVLNSWTDQDSKDSTYSMSSTLTL TKDEYERHNSYTCEATHKTSTSPIVKSFNRNEC 77 A5 HC human AA EVQLVESGGGVVQPGRSLRLSCAASGFTLSTYAMHWVRQAPGKGLEWVALISNDGSNKYY ADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARDRGLRFYFDYWGQGTTVTVSSA STKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSG LYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGP SVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNS TYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDEL TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQ QGNVFSCSVMHEALHNHYTQKSLSLSPGK 78 B9 HC human AA EVQLVESGGGLVQPGRSLRLSCAASGFTVSSYWMHWVRQAPGKGLEWVGFIRNKANGGTT EYAASVKGRFTISRDDSKNTLYLQMNSLRAEDTAVYYCARDRGLRFYFDYWGQGTTVTVS SASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQS SGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLG GPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQY NSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRD ELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSR WQQGNVFSCSVMHEALHNHYTQKSLSLSPGK 79 D8 HC human AA EVQLVESGGGVVQPGRSLRLSCAASGFTLSTYAMHWVRQAPGKGLEWVALISNDGSNKYY ADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCTRDRGLRFYFDYWGQGTTVTVSSA STKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSG LYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGP SVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNS TYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDEL TKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQ QGNVFSCSVMHEALHNHYTQKSLSLSPGK 80 A240 LC human AA QAVLTQPASLSASPGASASLTCTLRRGINVGAYSIYWYQQKPGSPPQYLLRYKSDSDKQQ GSGVSSRFSASKDASANAGILLISGLQSEDEADYYCMIWHSGASAVFGGGTKLTVLGQPK AAPSVTLFPPSSEELQANKATLVCLISDFYPGAVTVAWKADSSPVKAGVETTTPSKQSNN KYAASSYLSLTPEQWKSHKSYSCQVTHEGSTVEKTVAPTECS 81 5′-VL CEA I Bsu36I artificial Nt TTCTCTCCTTAGGTGTCCACTCCGACATTGAGCTCACCCAGTCTCC 82 3′-VL CEA I Xho I artificial Nt CATGCACTCGAG CTTGGTCCCTCCACCGAACGTC 83 5′-VL CEA II Bsu36I artificial Nt TTCTCTCCTTAGGTGTCCACTCCGACATTGTGCTGACCCAATCTCC 84 3′-VL CEA II Xho I artificial Nt CATGCACTCGAGCTTGGTCCCCCCACCGAACGTG 85 5′-VL CEA III Bsu36I artificial Nt TTCTCTCCTTAGGTGTCCACTCCGAGAACGTTCTCACCCAGTCTCC 86 3′-VL CEA III Xho I artificial Nt CATGCACTCGAGCTTGGTCCCAGCACCGAACGTG 87 5′-primer 5′-CEA I artificial Nt TTCTCTCCTTAGGTGTCCACTCCCAGGTCCAACTGCAGGAGTCAGG VH-Bsu36I 88 3′-primer 3′-CVH- artificial Nt GACTCACCTGAGGAGACGGTGACCGTGGTCCCTTGG Bsu36I 89 5′-primer 5′-CEA II artificial Nt TTCTCTCCTTAGGTGTCCACTCCGAGGTTCAGCTGCAGCAGTCTGG VH-Bsu36I 90 3′-primer 3′-CEA II artificial Nt GACTCACCTGAGGAGACGGTGACTGAGGTTCCTTGACC VH-Bsu36I 91 5′-primer 5′-CEA III artificial Nt TTCTCTCCTTAGGTGTCCACTCCCAGGTTAAGCTGCAGCAGTCTCC VH-Bsu36I 92 3′-primer 3′-CEA III artificial Nt GACTCACCTGAGGAGACTGTGACAGTGGTGCCTTGG VH-Bsu36I 93 5′-A240-Bsu36I artificial Nt TTCTCTCCTTAGGTGTCCACTCCCAGGCCGTGCTGACTCAGCCGGC 94 3′-A240-overlap artificial Nt GCCTTGGGCTGACCTAGGACGGTCAACTTGGTCC 95 5′-primer 5′-Clam- artificial Nt GTTGACCGTCCTAGGTCAGCCCAAGGCTGCCCCCTCG overlap 96 3′-primer 3′-Clam- artificial Nt GACGTAGCGGCCGCGTCGACCTATGAACATTCTGTAGGGGC NotI 97 5′-primer 5′-CVH- artificial Nt TTCTCTCCTTAGGTGTCCACTCCGAGGTGCAGCTGGTCGAGTC Bsu36I 98 3′-primer 3′-CVH- artificial Nt GACTCACCTGAGGAGACGGTGACCGTGGTCCCTTGG Bsu36I 99 CDR-H3* A5B7 artificial AA DX₁X₂X₃X₄FYFDY Kabat position 95 with “X₁”, “X₂”, “X₃” and “X₄” corresponding to Kabat corresponds to D; positions 96 (“X₁”), 97 (“X₂”), 98 (“X₃”) and 99 (“X₄”), Kabat positions 100, respectively, of CDR-H3 of murine monoclonal antibody A5B7 100a, 100b, 101, 102 and wherein “X” represents any amino acid residue. Pre- correspond to ferably, X represents residue “R” (Arginine), “G” (Glycine), FYFDY, respectively “L” (Leucine), “Y” (Tyrosine), “A” (Alanine), “D” (Aspartic acid), “S” (Serine), “W” (Tryptophan), “F” (Phenylalanine) or “T” (Threonine). More preferably, “X₁” is “R” (Arginine), “F” (Phenylalanine), “M” (Methionine), “E” (Glutamic acid), or “T” (Threonine); “X₂” represents preferably “G” (Glycine), “Y” (Tyrosine), “A” (Alanine), “D” (Aspartic acid), or “S” (Serine); “X₃”, represents preferably “L” (Leucine), “F” (Phenylalanine), “M” (Methionine), “E” (Glutamic acid), or “T” (Threonine); and “X₄” represents preferably “R” (Arginine), “Y” (Tyrosine), “A” (Alanine), “D” (Aspartic acid), or “S” (Serine). Abbreviations as used in the sequence listing of Table 1: AA = amino acid sequence Nt = nucleotide sequence HC = heavy chain LC = light chain Nucleotide sequence codes: B = C or G or T D = A or G or T H = A or C or T K = G or T M = A or C 

1. A pharmaceutical composition for the treatment of an epithelial tumor in a human, said pharmaceutical composition comprising an IgG1 antibody specifically binding to human CEA, wherein the variable region of said IgG1 antibody comprises at least the amino acid sequences selected from the group consisting of: (a) a CDR-H1 having the amino acid sequence “SYWMH” (SEQ ID NO. 29) and a CDR-H2 having the amino acid sequence “FIRNKANGGTTEYAASVKG” (SEQ ID NO. 28) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27) and (b) a CDR-H1 having the amino acid sequence “TYAMH” (SEQ ID NO. 31) and a CDR-H2 having the amino acid sequence “LISNDGSNKYYADSVKG” (SEQ ID NO. 30) and a CDR-H3 having the amino acid sequence “DRGLRFYFDY” (SEQ ID NO. 27).
 2. The pharmaceutical composition of claim 1, wherein said variable region comprises a CDR-L1 having the amino acid sequence “TLRRGINVGAYSIY” (SEQ ID NO. 34) and/or a CDR-L2 having the amino acid sequence “YKSDSDKQQGS” (SEQ ID NO. 33) and/or a CDR-L3 having the amino acid sequence “MIWHSGASAV” (SEQ ID NO. 32).
 3. The pharmaceutical composition of claim 1, wherein the light chain constant region of said IgG1 antibody is a lambda light chain constant region.
 4. The pharmaceutical composition of claim 1, wherein the amino acid sequence of the VH region of the variable region of said IgG1 antibody is SEQ ID NO. 20, 22 or
 24. 5. The pharmaceutical composition of claim 2, wherein the amino acid sequence of the VL region of the variable region of said IgG1 antibody is SEQ ID NO.
 26. 6. The pharmaceutical composition of claim 1, wherein the variable region of said IgG1 antibody is selected from the group consisting of: (a) the VH region consists of the amino acid sequence shown in SEQ ID NO. 22 and the VL region consists of the amino acid sequence shown in SEQ ID NO. 26; (b) the VH region consists of the amino acid sequence shown in SEQ ID NO. 20 and the VL region consists of the amino acid sequence shown in SEQ ID NO. 26; and (c) the VH region consists of the amino acid sequence shown in SEQ ID NO. 24 and the VL region consists of the amino acid sequence shown in SEQ ID NO.
 26. 7. The pharmaceutical composition of claim 1, wherein said IgG1 antibody comprises an amino acid sequence selected from the group consisting of: (a) an amino acid sequence of the heavy chain shown in SEQ ID NO. 77 and an amino acid sequence of the light chain shown in SEQ ID NO. 80; (b) an amino acid sequence of the heavy chain shown in SEQ ID NO. 78 and an amino acid sequence of the light chain shown in SEQ ID NO. 80; (c) an amino acid sequence of the heavy chain shown in SEQ ID NO. 79 and an amino acid sequence of the light chain shown in SEQ ID NO. 80; and an amino acid sequence at least 85% identical, more preferred at least 90% identical, most preferred at least 95% identical to the amino acid sequence of (a), (b) or (c).
 8. The pharmaceutical composition of claim 1, wherein said epithelial tumor is a gastrointestinal adenocarcinoma, a breast adenocarcinoma or a lung adenocarcinoma.
 9. The pharmaceutical composition of claim 8, wherein said gastrointestinal adenocarcinoma is a colorectal, pancreatic, an oesophageal or a gastric adenocarcinoma.
 10. The pharmaceutical composition of claim 1, wherein said pharmaceutical composition is for the treatment of progressive tumors, late stage tumors, tumor patients with high tumor load/burden, metastatic tumors, or tumor patients with a CEA serum concentration higher than 100 ng/ml.
 11. The pharmaceutical composition of claim 1, wherein the IgG1 antibody is CDR grafted, humanized and/or deimmunized.
 12. A pharmaceutical composition comprising a nucleic acid sequence encoding an IgG1 antibody as defined in claim
 1. 13. A pharmaceutical composition comprising a vector which comprises a nucleic acid sequence as defined in claim
 12. 14. A pharmaceutical composition comprising a vector which comprises a nucleic acid as defined in claim 12, wherein said vector further comprises a regulatory sequence which is operably linked to said nucleic acid sequence defined in claim
 12. 15. The pharmaceutical composition of claim 13, wherein said vector is an expression vector.
 16. A pharmaceutical composition comprising a host transformed or transfected with a nucleic acid defined in claim 12 or a vector which comprises a nucleic acid as defined in claim
 12. 17. A process for the production of a pharmaceutical composition according to claim 1, said process comprising culturing a host transformed or transfected with a nucleic acid sequence encoding an IgG1 antibody as defined in claim 1 under conditions allowing the expression of the IgG1 antibody as defined in claim 1 and recovering the produced IgG1 antibody from the culture.
 18. The pharmaceutical composition of claim 1, which is further comprising suitable formulations of carriers, stabilizers and/or excipients. 19.-23. (canceled)
 24. A method for the prevention, treatment or amelioration of an epithelial tumor in a subject in the need thereof, said method comprising the step of administration of an effective amount of a pharmaceutical composition claim 1, over a sufficient period of time.
 25. The method of claim 24, wherein said epithelial tumor is a gastrointestinal adenocarcinoma, a breast adenocarcinoma or a lung adenocarcinoma.
 26. The method of claim 25, wherein said gastrointestinal adenocarcinoma is a colorectal, pancreatic, an oesophageal or a gastric adenocarcinoma.
 27. The method of claim 24, wherein the pharmaceutical composition is for the treatment of progressive tumors, late stage tumors, tumor patients with high tumor load/burden, metastatic tumors, or tumor patients with a CEA serum concentration higher than 100 ng/ml.
 28. The method of claim 24, wherein said pharmaceutical composition is administered in combination with an additional drug.
 29. The method of claim 28, wherein said drug is a non-proteinaceous compound or a proteinaceous compound.
 30. A method for the prevention, treatment or amelioration of an epithelial tumor in a subject in the need thereof said method comprising the step of administration of an effective amount of a pharmaceutical composition claim 1, over a sufficient period of time, wherein said pharmaceutical composition is administered in combination with an additional drug, and wherein said proteinaceous compound or non-proteinaceous compound is administered simultaneously or non-simultaneously with an IgG1 antibody as defined in claim 1, a nucleic acid molecule, comprising a nucleic acid encoding an IgG1 antibody as defined in claim 1, a vector which comprises a nucleic acid sequence comprising a nucleic acid encoding an IgG1 antibody as defined in claim 1, or a host transformed or transfected with a nucleic acid sequence encoding an IgG1 antibody as defined in claim
 1. 31. The method of claim 24, wherein said subject is a human.
 32. A kit comprising an IgG1 antibody as defined in claim 1, a nucleic acid molecule comprising a nucleic acid encoding an IgG1 antibody as defined in claim 1, a vector which comprises a nucleic acid sequence comprising a nucleic acid encoding an IgG1 antibody as defined in claim 1, or a host transformed or transfected with a nucleic acid sequence encoding an IgG1 antibody as defined in claim
 1. 33. The pharmaceutical composition of claim 1, wherein said pharmaceutical composition is for the treatment of progressive tumors, late stage tumors, tumor patients with high tumor load/burden, metastatic tumors, or tumor patients with a CEA serum concentration higher than 100 ng/ml, or, a method for the prevention, treatment or amelioration of an epithelial tumor in a subject in the need thereof, said method comprising the step of administration of an effective amount of a pharmaceutical composition of claim 1, over a sufficient period of time, wherein the pharmaceutical composition is for the treatment of progressive tumors, late stage tumors, tumor patients with high tumor load/burden, metastatic tumors, or tumor patients with a CEA serum concentration higher than 100 ng/ml, and wherein said CEA serum concentration is determined by ELISA. 